add flashcard generation tooling and binary search cards

- gen-flashcards.py: auto-generate recognition cards from all problem files
- toolkit/gen-problem-cards.org: 199 auto-generated problem cards
- 5 binary search tool cards (std::binary_search, std::lower_bound, comparison, two-sum pattern, sorting gotcha)
- two-sum.org: add binary search C++ attempt
- lc-org.el: add doom emacs localleader keybinding support

org/study_deck_02/.dir-locals.el

@@ -1 +1,5 @@
-((org-mode . ((org-todo-keywords . ((sequence "TODO" | "DONE" "TOO_EASY"))))))
+((org-mode . ((org-todo-keywords . ((sequence "TODO" | "DONE" "TOO_EASY")))
+             (eval . (let ((lc-el (expand-file-name "lc-org.el" (dir-locals-find-file default-directory))))
+                       (when (and lc-el (file-exists-p lc-el))
+                         (load-file lc-el)
+                         (lc-org-mode 1)))))))

org/study_deck_02/AGENTS.md

@@ -14,7 +14,12 @@ An Anki-exportable study deck for NeetCode DSA problems.
    - Python and C++ solution stubs
    - A `NEETCODE` property linking back to the roadmap
 
-3. **Study flow** — open roadmap.org, pick a topic, pick a problem,
+3. **Toolkit** (`toolkit/`) — your reference library:
+   - `tricks.org` — flashcards for patterns & tricks (exported to Anki)
+   - `notes.org` — deep implementation notes with explanations (exported to Anki)
+   - `suggestions.org` — pattern reference for quick lookup (not exported)
+
+4. **Study flow** — open roadmap.org, pick a topic, pick a problem,
    follow the Notes link, solve it, mark it DONE in both places.
 
 ## File Layout
@@ -24,7 +29,10 @@ org/study_deck_02/
 ├── AGENTS.md                ← you are here
 ├── roadmap.org              ← generated by leetcode/extract.mjs
 ├── toolkit/
-│   └── tricks.org           ← common patterns & templates
+│   ├── tricks.org           ← flashcards for patterns & tricks
+│   ├── notes.org            ← deep implementation notes
+│   ├── suggestions.org      ← pattern reference (not exported)
+│   └── images/              ← diagrams, screenshots
 └── dsa/
     ├── arrays-hashing/
     │   ├── 0217-contains-duplicate.org

org/study_deck_02/add-lc-problem.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+"""Add :lc-problem <number> to org source blocks in leetcode problem files."""
+
+import re
+import sys
+from pathlib import Path
+
+
+def process_file(path: Path, dry_run: bool = False) -> bool:
+    """Add :lc-problem to src blocks that don't already have it. Returns True if modified."""
+    m = re.match(r"(\d{4})-", path.stem)
+    if not m:
+        return False
+    problem_num = str(int(m.group(1)))  # strip leading zeros: "0015" -> "15"
+
+    text = path.read_text()
+    original = text
+
+    # Match #+begin_src <lang> where lang is python or cpp
+    def fix_src_block(match: re.Match) -> str:
+        full = match.group(0)
+        lang = match.group(1)
+        suffix = match.group(2) or ""
+
+        # If already has :lc-problem, fix leading zeros
+        if ":lc-problem" in suffix:
+            suffix = re.sub(r":lc-problem 0+(\d)", rf":lc-problem \1", suffix)
+            return f"#+begin_src {lang}{suffix}"
+
+        # Add :lc-problem
+        extra = f" :lc-problem {problem_num}"
+        if lang == "python":
+            extra += " :lc-lang python3"
+        return f"#+begin_src {lang}{extra}{suffix}"
+
+    text = re.sub(
+        r"#\+begin_src (python|cpp)([^\n]*)",
+        fix_src_block,
+        text,
+    )
+
+    if text != original:
+        if dry_run:
+            print(f"  would modify: {path.name}")
+        else:
+            path.write_text(text)
+            print(f"  modified: {path.name}")
+        return True
+    return False
+
+
+def main():
+    dry_run = "--dry-run" in sys.argv
+    base = Path(__file__).parent / "dsa"
+    if not base.exists():
+        print(f"dsa/ directory not found at {base}")
+        sys.exit(1)
+
+    org_files = sorted(base.rglob("*.org"))
+    print(f"Found {len(org_files)} org files in dsa/")
+
+    modified = 0
+    skipped = 0
+    for f in org_files:
+        if process_file(f, dry_run):
+            modified += 1
+        else:
+            skipped += 1
+
+    print(f"\nDone: {modified} modified, {skipped} unchanged")
+
+
+if __name__ == "__main__":
+    main()

org/study_deck_02/dsa/1-d-dynamic-programming/0005-longest-palindromic-substring.org

@@ -35,13 +35,13 @@ Output: "bb"
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 5 :lc-lang python3
 class Solution:
     def longestPalindrome(self, s: str) -> str:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 5
 class Solution {
 public:
     string longestPalindrome(string s) {

org/study_deck_02/dsa/1-d-dynamic-programming/0070-climbing-stairs.org

@@ -41,13 +41,13 @@ Explanation: There are three ways to climb to the top.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 70 :lc-lang python3
 class Solution:
     def climbStairs(self, n: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 70
 class Solution {
 public:
     int climbStairs(int n) {

org/study_deck_02/dsa/1-d-dynamic-programming/0091-decode-ways.org

@@ -72,13 +72,13 @@ The test cases are generated so that the answer fits in a *32-bit* integer.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 91 :lc-lang python3
 class Solution:
     def numDecodings(self, s: str) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 91
 class Solution {
 public:
     int numDecodings(string s) {

org/study_deck_02/dsa/1-d-dynamic-programming/0139-word-break.org

@@ -54,13 +54,13 @@ Output: false
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 139 :lc-lang python3
 class Solution:
     def wordBreak(self, s: str, wordDict: List[str]) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 139
 class Solution {
 public:
     bool wordBreak(string s, vector<string>& wordDict) {

org/study_deck_02/dsa/1-d-dynamic-programming/0152-maximum-product-subarray.org

@@ -42,13 +42,13 @@ Explanation: The result cannot be 2, because [-2,-1] is not a subarray.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 152 :lc-lang python3
 class Solution:
     def maxProduct(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 152
 class Solution {
 public:
     int maxProduct(vector<int>& nums) {

org/study_deck_02/dsa/1-d-dynamic-programming/0198-house-robber.org

@@ -40,13 +40,13 @@ Total amount you can rob = 2 + 9 + 1 = 12.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 198 :lc-lang python3
 class Solution:
     def rob(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 198
 class Solution {
 public:
     int rob(vector<int>& nums) {

org/study_deck_02/dsa/1-d-dynamic-programming/0213-house-robber-ii.org

@@ -48,13 +48,13 @@ Output: 3
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 213 :lc-lang python3
 class Solution:
     def rob(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 213
 class Solution {
 public:
     int rob(vector<int>& nums) {

org/study_deck_02/dsa/1-d-dynamic-programming/0300-longest-increasing-subsequence.org

@@ -46,13 +46,13 @@ Follow up: Can you come up with an algorithm that runs in ~O(n log(n))~ time com
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 300 :lc-lang python3
 class Solution:
     def lengthOfLIS(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 300
 class Solution {
 public:
     int lengthOfLIS(vector<int>& nums) {

org/study_deck_02/dsa/1-d-dynamic-programming/0322-coin-change.org

@@ -50,13 +50,13 @@ Output: 0
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 322 :lc-lang python3
 class Solution:
     def coinChange(self, coins: List[int], amount: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 322
 class Solution {
 public:
     int coinChange(vector<int>& coins, int amount) {

org/study_deck_02/dsa/1-d-dynamic-programming/0416-partition-equal-subset-sum.org

@@ -36,13 +36,13 @@ Explanation: The array cannot be partitioned into equal sum subsets.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 416 :lc-lang python3
 class Solution:
     def canPartition(self, nums: List[int]) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 416
 class Solution {
 public:
     bool canPartition(vector<int>& nums) {

org/study_deck_02/dsa/1-d-dynamic-programming/0647-palindromic-substrings.org

@@ -40,13 +40,13 @@ Explanation: Six palindromic strings: "a", "a", "a", "aa", "aa", "aaa".
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 647 :lc-lang python3
 class Solution:
     def countSubstrings(self, s: str) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 647
 class Solution {
 public:
     int countSubstrings(string s) {

org/study_deck_02/dsa/1-d-dynamic-programming/0656-coin-path.org

@@ -8,11 +8,11 @@
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 656 :lc-lang python3
 
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 656
 
 #+end_src

org/study_deck_02/dsa/1-d-dynamic-programming/0746-min-cost-climbing-stairs.org

@@ -49,13 +49,13 @@ The total cost is 6.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 746 :lc-lang python3
 class Solution:
     def minCostClimbingStairs(self, cost: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 746
 class Solution {
 public:
     int minCostClimbingStairs(vector<int>& cost) {

org/study_deck_02/dsa/2-d-dynamic-programming/0010-regular-expression-matching.org

@@ -58,13 +58,13 @@ Explanation: ".*" means "zero or more (*) of any character (.)".
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 10 :lc-lang python3
 class Solution:
     def isMatch(self, s: str, p: str) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 10
 class Solution {
 public:
     bool isMatch(string s, string p) {

org/study_deck_02/dsa/2-d-dynamic-programming/0062-unique-paths.org

@@ -40,13 +40,13 @@ Explanation: From the top-left corner, there are a total of 3 ways to reach the
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 62 :lc-lang python3
 class Solution:
     def uniquePaths(self, m: int, n: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 62
 class Solution {
 public:
     int uniquePaths(int m, int n) {

org/study_deck_02/dsa/2-d-dynamic-programming/0072-edit-distance.org

@@ -52,13 +52,13 @@ exection -> execution (insert 'u')
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 72 :lc-lang python3
 class Solution:
     def minDistance(self, word1: str, word2: str) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 72
 class Solution {
 public:
     int minDistance(string word1, string word2) {

org/study_deck_02/dsa/2-d-dynamic-programming/0097-interleaving-string.org

@@ -64,13 +64,13 @@ Output: true
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 97 :lc-lang python3
 class Solution:
     def isInterleave(self, s1: str, s2: str, s3: str) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 97
 class Solution {
 public:
     bool isInterleave(string s1, string s2, string s3) {

org/study_deck_02/dsa/2-d-dynamic-programming/0115-distinct-subsequences.org

@@ -48,13 +48,13 @@ babgbag
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 115 :lc-lang python3
 class Solution:
     def numDistinct(self, s: str, t: str) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 115
 class Solution {
 public:
     int numDistinct(string s, string t) {

org/study_deck_02/dsa/2-d-dynamic-programming/0309-best-time-to-buy-and-sell-stock-with-cooldown.org

@@ -41,13 +41,13 @@ Output: 0
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 309 :lc-lang python3
 class Solution:
     def maxProfit(self, prices: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 309
 class Solution {
 public:
     int maxProfit(vector<int>& prices) {

org/study_deck_02/dsa/2-d-dynamic-programming/0312-burst-balloons.org

@@ -43,13 +43,13 @@ Output: 10
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 312 :lc-lang python3
 class Solution:
     def maxCoins(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 312
 class Solution {
 public:
     int maxCoins(vector<int>& nums) {

org/study_deck_02/dsa/2-d-dynamic-programming/0329-longest-increasing-path-in-a-matrix.org

@@ -51,13 +51,13 @@ Output: 1
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 329 :lc-lang python3
 class Solution:
     def longestIncreasingPath(self, matrix: List[List[int]]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 329
 class Solution {
 public:
     int longestIncreasingPath(vector<vector<int>>& matrix) {

org/study_deck_02/dsa/2-d-dynamic-programming/0494-target-sum.org

@@ -50,13 +50,13 @@ Output: 1
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 494 :lc-lang python3
 class Solution:
     def findTargetSumWays(self, nums: List[int], target: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 494
 class Solution {
 public:
     int findTargetSumWays(vector<int>& nums, int target) {

org/study_deck_02/dsa/2-d-dynamic-programming/0518-coin-change-ii.org

@@ -59,13 +59,13 @@ Output: 1
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 518 :lc-lang python3
 class Solution:
     def change(self, amount: int, coins: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 518
 class Solution {
 public:
     int change(int amount, vector<int>& coins) {

org/study_deck_02/dsa/2-d-dynamic-programming/1143-longest-common-subsequence.org

@@ -52,13 +52,13 @@ Explanation: There is no such common subsequence, so the result is 0.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1143 :lc-lang python3
 class Solution:
     def longestCommonSubsequence(self, text1: str, text2: str) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1143
 class Solution {
 public:
     int longestCommonSubsequence(string text1, string text2) {

org/study_deck_02/dsa/2-d-dynamic-programming/1220-count-vowels-permutation.org

@@ -57,13 +57,13 @@ Output: 68
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1220 :lc-lang python3
 class Solution:
     def countVowelPermutation(self, n: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1220
 class Solution {
 public:
     int countVowelPermutation(int n) {

org/study_deck_02/dsa/2-d-dynamic-programming/1911-maximum-alternating-subsequence-sum.org

@@ -52,13 +52,13 @@ Explanation: It is optimal to choose the subsequence [6,1,5] with alternating su
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1911 :lc-lang python3
 class Solution:
     def maxAlternatingSum(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1911
 class Solution {
 public:
     long long maxAlternatingSum(vector<int>& nums) {

org/study_deck_02/dsa/advanced-graphs/0269-alien-dictionary.org

@@ -8,11 +8,11 @@
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 269 :lc-lang python3
 
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 269
 
 #+end_src

org/study_deck_02/dsa/advanced-graphs/0332-reconstruct-itinerary.org

@@ -49,13 +49,13 @@ Explanation: Another possible reconstruction is ["JFK","SFO","ATL","JFK","ATL","
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 332 :lc-lang python3
 class Solution:
     def findItinerary(self, tickets: List[List[str]]) -> List[str]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 332
 class Solution {
 public:
     vector<string> findItinerary(vector<vector<string>>& tickets) {

org/study_deck_02/dsa/advanced-graphs/0743-network-delay-time.org

@@ -55,13 +55,13 @@ Output: -1
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 743 :lc-lang python3
 class Solution:
     def networkDelayTime(self, times: List[List[int]], n: int, k: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 743
 class Solution {
 public:
     int networkDelayTime(vector<vector<int>>& times, int n, int k) {

org/study_deck_02/dsa/advanced-graphs/0778-swim-in-rising-water.org

@@ -53,13 +53,13 @@ We need to wait until time 16 so that (0, 0) and (4, 4) are connected.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 778 :lc-lang python3
 class Solution:
     def swimInWater(self, grid: List[List[int]]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 778
 class Solution {
 public:
     int swimInWater(vector<vector<int>>& grid) {

org/study_deck_02/dsa/advanced-graphs/0787-cheapest-flights-within-k-stops.org

@@ -69,13 +69,13 @@ The optimal path with no stops from city 0 to 2 is marked in red and has cost 50
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 787 :lc-lang python3
 class Solution:
     def findCheapestPrice(self, n: int, flights: List[List[int]], src: int, dst: int, k: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 787
 class Solution {
 public:
     int findCheapestPrice(int n, vector<vector<int>>& flights, int src, int dst, int k) {

org/study_deck_02/dsa/advanced-graphs/1584-min-cost-to-connect-all-points.org

@@ -44,13 +44,13 @@ Output: 18
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1584 :lc-lang python3
 class Solution:
     def minCostConnectPoints(self, points: List[List[int]]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1584
 class Solution {
 public:
     int minCostConnectPoints(vector<vector<int>>& points) {

org/study_deck_02/dsa/advanced-graphs/2493-divide-nodes-into-the-maximum-number-of-groups.org

@@ -61,13 +61,13 @@ It can be shown that no grouping is possible.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 2493 :lc-lang python3
 class Solution:
     def magnificentSets(self, n: int, edges: List[List[int]]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 2493
 class Solution {
 public:
     int magnificentSets(int n, vector<vector<int>>& edges) {

org/study_deck_02/dsa/advanced-graphs/2812-find-the-safest-path-in-a-grid.org

@@ -69,13 +69,13 @@ It can be shown that there are no other paths with a higher safeness factor.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 2812 :lc-lang python3
 class Solution:
     def maximumSafenessFactor(self, grid: List[List[int]]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 2812
 class Solution {
 public:
     int maximumSafenessFactor(vector<vector<int>>& grid) {

org/study_deck_02/dsa/arrays-hashing/0001-two-sum.org

@@ -54,17 +54,40 @@ Output: [0,1]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1 :lc-lang python3
 class Solution:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
+        sb = {}
+        for xi, x in enumerate(nums):
+            want = target - x;
+            if want in sb:
+                return sb[want], xi
+            sb[x] = xi
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1
+#include <algorithm>
 class Solution {
 public:
-    vector<int> twoSum(vector<int>& nums, int target) {
-        
+  vector<int> twoSum(vector<int>& nums, int target) {
+    std::sort(nums.begin(), nums.end());
+    for (int i=0; i< nums.size(); i++) {
+      int x = nums[i];
+      if (x > target) {
+        return {};
+      }
+      // TODO: c++ binary search, i forgot how to do this
+      int want = target - x
+      auto it = std::binary_learch(nums.begin() + i + 1, nums.end(), want);
+      if (it != nums.end() && *it == want) {
+        int wi = std::distance(nums.begin(), it)
+        return {i, wi}
+      }
     }
+    reuturn {};
+  }
 };
 #+end_src
+
+#+RESULTS:

org/study_deck_02/dsa/arrays-hashing/0036-valid-sudoku.org

@@ -67,13 +67,13 @@ Explanation: Same as Example 1, except with the 5 in the top left corner being m
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 36 :lc-lang python3
 class Solution:
     def isValidSudoku(self, board: List[List[str]]) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 36
 class Solution {
 public:
     bool isValidSudoku(vector<vector<char>>& board) {

org/study_deck_02/dsa/arrays-hashing/0049-group-anagrams.org

@@ -44,13 +44,13 @@ Given an array of strings ~strs~, group the anagrams together. You can return th
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 49 :lc-lang python3
 class Solution:
     def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 49
 class Solution {
 public:
     vector<vector<string>> groupAnagrams(vector<string>& strs) {

org/study_deck_02/dsa/arrays-hashing/0128-longest-consecutive-sequence.org

@@ -46,13 +46,13 @@ Output: 3
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 128 :lc-lang python3
 class Solution:
     def longestConsecutive(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 128
 class Solution {
 public:
     int longestConsecutive(vector<int>& nums) {

org/study_deck_02/dsa/arrays-hashing/0217-contains-duplicate.org

@@ -42,7 +42,7 @@ All elements are distinct.
 Write your approach here.
 
 ** DONE Python
-#+begin_src python
+#+begin_src python :lc-problem 217 :lc-lang python3
 class Solution:
     def containsDuplicate(self, nums: List[int]) -> bool:
         s = set()
@@ -54,7 +54,7 @@ class Solution:
 #+end_src
 
 ** DONE C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 217
 #include <vector>
 #include <set>
 class Solution {

org/study_deck_02/dsa/arrays-hashing/0238-product-of-array-except-self.org

@@ -40,13 +40,13 @@ Output: [0,0,9,0,0]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 238 :lc-lang python3
 class Solution:
     def productExceptSelf(self, nums: List[int]) -> List[int]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 238
 class Solution {
 public:
     vector<int> productExceptSelf(vector<int>& nums) {

org/study_deck_02/dsa/arrays-hashing/0242-valid-anagram.org

@@ -30,13 +30,13 @@ Given two strings ~s~ and ~t~, return ~true~ if ~t~ is an anagram of ~s~, and ~f
 Write your approach here.
 
 ** DONE Python
-#+begin_src python
+#+begin_src python :lc-problem 242 :lc-lang python3
 class Solution:
     def isAnagram(self, s: str, t: str) -> bool:
 #+end_src
 
 ** DONE C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 242
 #include <map>
 #include <string>
 class Solution {

org/study_deck_02/dsa/arrays-hashing/0271-encode-and-decode-strings.org

@@ -8,11 +8,11 @@
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 271 :lc-lang python3
 
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 271
 
 #+end_src

org/study_deck_02/dsa/arrays-hashing/0347-top-k-frequent-elements.org

@@ -40,13 +40,15 @@ Given an integer array ~nums~ and an integer ~k~, return /the/ ~k~ /most frequen
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 347 :lc-lang python3
 class Solution:
     def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        from collections import Counter
+        return [n for n, _ in Counter(nums).most_common(k)]
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 347
 class Solution {
 public:
     vector<int> topKFrequent(vector<int>& nums, int k) {

org/study_deck_02/dsa/arrays-hashing/1408-string-matching-in-an-array.org

@@ -51,13 +51,43 @@ Explanation: No string of words is substring of another string.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1408 :lc-lang python3
+from collections import defaultdict as dd
 class Solution:
     def stringMatching(self, words: List[str]) -> List[str]:
+        words = reversed(sorted(words))
+        def squash(word, trie):
+            lst = []
+            for c in word:
+                lst.append([trie, ''])
+                for i in range(len(lst)):
+                    lst[i][0] = lst[i][0][c]
+                    lst[i][1] += c
+                    if not lst[i][0]['ads']:
+                        lst[i][0]['ads'] = {lst[i][1]: [word]}
+                    else:
+                        lst[i][0]['ads'][lst[i][1]].append(word)
+        def in_trie(word, trie):
+            for c in word:
+                if c not in trie:
+                    return []
+                trie = trie[c]
+            return [(word, bw) for bw in trie['ads'][word]]
+        trie_maker = lambda: dd(trie_maker)
+        trie = trie_maker()
+        ans = []
+        for s in words:
+            ans += in_trie(s, trie)
+            squash(s, trie)
+        return ans
+
+
 #+end_src
 
+**
+
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1408
 class Solution {
 public:
     vector<string> stringMatching(vector<string>& words) {

org/study_deck_02/dsa/arrays-hashing/1769-minimum-number-of-operations-to-move-all-balls-to-each-box.org

@@ -46,13 +46,13 @@ Output: [11,8,5,4,3,4]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1769 :lc-lang python3
 class Solution:
     def minOperations(self, boxes: str) -> List[int]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1769
 class Solution {
 public:
     vector<int> minOperations(string boxes) {

org/study_deck_02/dsa/arrays-hashing/2678-number-of-senior-citizens.org

@@ -52,13 +52,13 @@ Explanation: None of the passengers are older than 60.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 2678 :lc-lang python3
 class Solution:
     def countSeniors(self, details: List[str]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 2678
 class Solution {
 public:
     int countSeniors(vector<string>& details) {

org/study_deck_02/dsa/backtracking/0017-letter-combinations-of-a-phone-number.org

@@ -36,13 +36,13 @@ Output: ["a","b","c"]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 17 :lc-lang python3
 class Solution:
     def letterCombinations(self, digits: str) -> List[str]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 17
 class Solution {
 public:
     vector<string> letterCombinations(string digits) {

org/study_deck_02/dsa/backtracking/0022-generate-parentheses.org

@@ -30,13 +30,13 @@ Output: ["()"]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 22 :lc-lang python3
 class Solution:
     def generateParenthesis(self, n: int) -> List[str]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 22
 class Solution {
 public:
     vector<string> generateParenthesis(int n) {

org/study_deck_02/dsa/backtracking/0039-combination-sum.org

@@ -55,13 +55,13 @@ Output: []
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 39 :lc-lang python3
 class Solution:
     def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 39
 class Solution {
 public:
     vector<vector<int>> combinationSum(vector<int>& candidates, int target) {

org/study_deck_02/dsa/backtracking/0040-combination-sum-ii.org

@@ -50,13 +50,13 @@ Output:
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 40 :lc-lang python3
 class Solution:
     def combinationSum2(self, candidates: List[int], target: int) -> List[List[int]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 40
 class Solution {
 public:
     vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {

org/study_deck_02/dsa/backtracking/0046-permutations.org

@@ -41,13 +41,13 @@ Output: [[1]]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 46 :lc-lang python3
 class Solution:
     def permute(self, nums: List[int]) -> List[List[int]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 46
 class Solution {
 public:
     vector<vector<int>> permute(vector<int>& nums) {

org/study_deck_02/dsa/backtracking/0051-n-queens.org

@@ -37,13 +37,13 @@ Output: [["Q"]]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 51 :lc-lang python3
 class Solution:
     def solveNQueens(self, n: int) -> List[List[str]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 51
 class Solution {
 public:
     vector<vector<string>> solveNQueens(int n) {

org/study_deck_02/dsa/backtracking/0052-n-queens-ii.org

@@ -35,13 +35,13 @@ Output: 1
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 52 :lc-lang python3
 class Solution:
     def totalNQueens(self, n: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 52
 class Solution {
 public:
     int totalNQueens(int n) {

org/study_deck_02/dsa/backtracking/0077-combinations.org

@@ -39,13 +39,13 @@ Explanation: There is 1 choose 1 = 1 total combination.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 77 :lc-lang python3
 class Solution:
     def combine(self, n: int, k: int) -> List[List[int]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 77
 class Solution {
 public:
     vector<vector<int>> combine(int n, int k) {

org/study_deck_02/dsa/backtracking/0078-subsets.org

@@ -38,13 +38,13 @@ Output: [[],[0]]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 78 :lc-lang python3
 class Solution:
     def subsets(self, nums: List[int]) -> List[List[int]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 78
 class Solution {
 public:
     vector<vector<int>> subsets(vector<int>& nums) {

org/study_deck_02/dsa/backtracking/0079-word-search.org

@@ -53,13 +53,13 @@ Output: false
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 79 :lc-lang python3
 class Solution:
     def exist(self, board: List[List[str]], word: str) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 79
 class Solution {
 public:
     bool exist(vector<vector<char>>& board, string word) {

org/study_deck_02/dsa/backtracking/0090-subsets-ii.org

@@ -34,13 +34,13 @@ Output: [[],[0]]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 90 :lc-lang python3
 class Solution:
     def subsetsWithDup(self, nums: List[int]) -> List[List[int]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 90
 class Solution {
 public:
     vector<vector<int>> subsetsWithDup(vector<int>& nums) {

org/study_deck_02/dsa/backtracking/0131-palindrome-partitioning.org

@@ -32,13 +32,13 @@ Output: [["a"]]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 131 :lc-lang python3
 class Solution:
     def partition(self, s: str) -> List[List[str]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 131
 class Solution {
 public:
     vector<vector<string>> partition(string s) {

org/study_deck_02/dsa/backtracking/0351-android-unlock-patterns.org

@@ -8,11 +8,11 @@
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 351 :lc-lang python3
 
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 351
 
 #+end_src

org/study_deck_02/dsa/backtracking/1079-letter-tile-possibilities.org

@@ -46,13 +46,13 @@ Output: 1
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1079 :lc-lang python3
 class Solution:
     def numTilePossibilities(self, tiles: str) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1079
 class Solution {
 public:
     int numTilePossibilities(string tiles) {

org/study_deck_02/dsa/backtracking/1863-sum-of-all-subsets-xor-total.org

@@ -8,11 +8,11 @@
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 1863 :lc-lang python3
 
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 1863
 
 #+end_src

org/study_deck_02/dsa/binary-search/0004-median-of-two-sorted-arrays.org

@@ -46,13 +46,13 @@ Explanation: merged array = [1,2,3,4] and median is (2 + 3) / 2 = 2.5.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 4 :lc-lang python3
 class Solution:
     def findMedianSortedArrays(self, nums1: List[int], nums2: List[int]) -> float:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 4
 class Solution {
 public:
     double findMedianSortedArrays(vector<int>& nums1, vector<int>& nums2) {

org/study_deck_02/dsa/binary-search/0033-search-in-rotated-sorted-array.org

@@ -51,13 +51,13 @@ Output: -1
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 33 :lc-lang python3
 class Solution:
     def search(self, nums: List[int], target: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 33
 class Solution {
 public:
     int search(vector<int>& nums, int target) {

org/study_deck_02/dsa/binary-search/0074-search-a-2d-matrix.org

@@ -46,13 +46,13 @@ Output: false
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 74 :lc-lang python3
 class Solution:
     def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 74
 class Solution {
 public:
     bool searchMatrix(vector<vector<int>>& matrix, int target) {

org/study_deck_02/dsa/binary-search/0153-find-minimum-in-rotated-sorted-array.org

@@ -62,13 +62,13 @@ Explanation: The original array was [11,13,15,17] and it was rotated 4 times.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 153 :lc-lang python3
 class Solution:
     def findMin(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 153
 class Solution {
 public:
     int findMin(vector<int>& nums) {

org/study_deck_02/dsa/binary-search/0704-binary-search.org

@@ -42,13 +42,13 @@ Explanation: 2 does not exist in nums so return -1
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 704 :lc-lang python3
 class Solution:
     def search(self, nums: List[int], target: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 704
 class Solution {
 public:
     int search(vector<int>& nums, int target) {

org/study_deck_02/dsa/binary-search/0719-find-k-th-smallest-pair-distance.org

@@ -54,13 +54,13 @@ Output: 5
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 719 :lc-lang python3
 class Solution:
     def smallestDistancePair(self, nums: List[int], k: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 719
 class Solution {
 public:
     int smallestDistancePair(vector<int>& nums, int k) {

org/study_deck_02/dsa/binary-search/0875-koko-eating-bananas.org

@@ -51,13 +51,13 @@ Output: 23
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 875 :lc-lang python3
 class Solution:
     def minEatingSpeed(self, piles: List[int], h: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 875
 class Solution {
 public:
     int minEatingSpeed(vector<int>& piles, int h) {

org/study_deck_02/dsa/binary-search/0981-time-based-key-value-store.org

@@ -51,7 +51,7 @@ timeMap.get("foo", 5);         // return "bar2"
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 981 :lc-lang python3
 class TimeMap:
 
     def __init__(self):
@@ -71,7 +71,7 @@ class TimeMap:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 981
 class TimeMap {
 public:
     TimeMap() {

org/study_deck_02/dsa/binary-search/2300-successful-pairs-of-spells-and-potions.org

@@ -54,13 +54,13 @@ Thus, [2,0,2] is returned.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 2300 :lc-lang python3
 class Solution:
     def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 2300
 class Solution {
 public:
     vector<int> successfulPairs(vector<int>& spells, vector<int>& potions, long long success) {

org/study_deck_02/dsa/binary-search/lower-bound-vs-binary-search.org

@@ -0,0 +1,11 @@
+#+ANKI_DECK: study_deck_02
+* When to use lower_bound vs binary_search :cpp:binary-search:algorithm:retrieval::recognition:
+:PROPERTIES:
+:END:
+
+** Front
+When should you use ~std::lower_bound~ instead of ~std::binary_search~?
+
+** Back
+Use ~lower_bound~ when you need the *position/index* of the element.
+Use ~binary_search~ when you only need to know *if it exists* (bool).

org/study_deck_02/dsa/binary-search/sorting-destroys-indices.org

@@ -0,0 +1,10 @@
+#+ANKI_DECK: study_deck_02
+* Two Sum gotcha: sorting destroys original indices :cpp:two-sum:binary-search:retrieval::recognition:
+:PROPERTIES:
+:END:
+
+** Front
+If you sort ~nums~ in-place for Two Sum, what goes wrong?
+
+** Back
+Sorting changes the indices. If the problem requires returning *original* indices, store ~{value, original_index}~ pairs before sorting.

org/study_deck_02/dsa/binary-search/std-binary-search.org

@@ -0,0 +1,14 @@
+#+ANKI_DECK: study_deck_02
+* std::binary_search: check element exists :cpp:binary-search:algorithm:retrieval::recognition:
+:PROPERTIES:
+:END:
+
+** Front
+What does ~std::binary_search~ return, and what must the range be?
+
+** Back
+Returns ~bool~ (true if element found). The range must be *sorted*.
+
+#+begin_src cpp
+bool found = std::binary_search(vec.begin(), vec.end(), value);
+#+end_src

org/study_deck_02/dsa/binary-search/std-lower-bound.org

@@ -0,0 +1,14 @@
+#+ANKI_DECK: study_deck_02
+* std::lower_bound: find position of element :cpp:binary-search:algorithm:retrieval::recognition:
+:PROPERTIES:
+:END:
+
+** Front
+What does ~std::lower_bound~ return?
+
+** Back
+An iterator to the first element *>=* the given value. Returns ~end()~ if no such element exists.
+
+#+begin_src cpp
+auto it = std::lower_bound(vec.begin(), vec.end(), value);
+#+end_src

org/study_deck_02/dsa/binary-search/two-sum-lower-bound.org

@@ -0,0 +1,16 @@
+#+ANKI_DECK: study_deck_02
+* Task: Two Sum complement lookup with lower_bound :cpp:binary-search:two-sum:retrieval::production:
+:PROPERTIES:
+:END:
+
+** Front
+Given sorted ~nums~ and index ~i~, write C++ to check if ~target - nums[i]~ exists in the rest of the array using ~std::lower_bound~.
+
+** Back
+#+begin_src cpp
+int complement = target - nums[i];
+auto it = std::lower_bound(nums.begin() + i + 1, nums.end(), complement);
+if (it != nums.end() && *it == complement) {
+    return {(int)i, (int)std::distance(nums.begin(), it)};
+}
+#+end_src

org/study_deck_02/dsa/bit-manipulation/0007-reverse-integer.org

@@ -43,13 +43,13 @@ Output: 21
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 7 :lc-lang python3
 class Solution:
     def reverse(self, x: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 7
 class Solution {
 public:
     int reverse(int x) {

org/study_deck_02/dsa/bit-manipulation/0136-single-number.org

@@ -38,13 +38,13 @@ You must implement a solution with a linear runtime complexity and use only cons
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 136 :lc-lang python3
 class Solution:
     def singleNumber(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 136
 class Solution {
 public:
     int singleNumber(vector<int>& nums) {

org/study_deck_02/dsa/bit-manipulation/0190-reverse-bits.org

@@ -52,13 +52,13 @@ Reverse bits of a given 32 bits signed integer.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 190 :lc-lang python3
 class Solution:
     def reverseBits(self, n: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 190
 class Solution {
 public:
     int reverseBits(int n) {

org/study_deck_02/dsa/bit-manipulation/0191-number-of-1-bits.org

@@ -46,13 +46,13 @@ The input binary string *1111111111111111111111111111101* has a total of thirty
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 191 :lc-lang python3
 class Solution:
     def hammingWeight(self, n: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 191
 class Solution {
 public:
     int hammingWeight(int n) {

org/study_deck_02/dsa/bit-manipulation/0231-power-of-two.org

@@ -47,13 +47,13 @@ Output: false
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 231 :lc-lang python3
 class Solution:
     def isPowerOfTwo(self, n: int) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 231
 class Solution {
 public:
     bool isPowerOfTwo(int n) {

org/study_deck_02/dsa/bit-manipulation/0260-single-number-iii.org

@@ -48,13 +48,13 @@ Output: [1,0]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 260 :lc-lang python3
 class Solution:
     def singleNumber(self, nums: List[int]) -> List[int]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 260
 class Solution {
 public:
     vector<int> singleNumber(vector<int>& nums) {

org/study_deck_02/dsa/bit-manipulation/0268-missing-number.org

@@ -52,13 +52,13 @@ Given an array ~nums~ containing ~n~ distinct numbers in the range ~[0, n]~, ret
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 268 :lc-lang python3
 class Solution:
     def missingNumber(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 268
 class Solution {
 public:
     int missingNumber(vector<int>& nums) {

org/study_deck_02/dsa/bit-manipulation/0338-counting-bits.org

@@ -49,13 +49,13 @@ Explanation:
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 338 :lc-lang python3
 class Solution:
     def countBits(self, n: int) -> List[int]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 338
 class Solution {
 public:
     vector<int> countBits(int n) {

org/study_deck_02/dsa/bit-manipulation/0371-sum-of-two-integers.org

@@ -30,13 +30,13 @@ Output: 5
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 371 :lc-lang python3
 class Solution:
     def getSum(self, a: int, b: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 371
 class Solution {
 public:
     int getSum(int a, int b) {

org/study_deck_02/dsa/bit-manipulation/2220-minimum-bit-flips-to-convert-number.org

@@ -48,13 +48,13 @@ It can be shown we cannot convert 3 to 4 in less than 3 steps. Hence, we return
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 2220 :lc-lang python3
 class Solution:
     def minBitFlips(self, start: int, goal: int) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 2220
 class Solution {
 public:
     int minBitFlips(int start, int goal) {

org/study_deck_02/dsa/graphs/0127-word-ladder.org

@@ -54,13 +54,13 @@ Explanation: The endWord "cog" is not in wordList, therefore there is no valid t
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 127 :lc-lang python3
 class Solution:
     def ladderLength(self, beginWord: str, endWord: str, wordList: List[str]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 127
 class Solution {
 public:
     int ladderLength(string beginWord, string endWord, vector<string>& wordList) {

org/study_deck_02/dsa/graphs/0130-surrounded-regions.org

@@ -44,7 +44,7 @@ In the above diagram, the bottom region is not captured because it is on the edg
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 130 :lc-lang python3
 class Solution:
     def solve(self, board: List[List[str]]) -> None:
         """
@@ -53,7 +53,7 @@ class Solution:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 130
 class Solution {
 public:
     void solve(vector<vector<char>>& board) {

org/study_deck_02/dsa/graphs/0133-clone-graph.org

@@ -77,7 +77,7 @@ Explanation: This an empty graph, it does not have any nodes.
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 133 :lc-lang python3
 """
 # Definition for a Node.
 class Node:
@@ -92,7 +92,7 @@ class Solution:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 133
 /*
 // Definition for a Node.
 class Node {

org/study_deck_02/dsa/graphs/0200-number-of-islands.org

@@ -50,13 +50,13 @@ Output: 3
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 200 :lc-lang python3
 class Solution:
     def numIslands(self, grid: List[List[str]]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 200
 class Solution {
 public:
     int numIslands(vector<vector<char>>& grid) {

org/study_deck_02/dsa/graphs/0207-course-schedule.org

@@ -48,13 +48,13 @@ To take course 1 you should have finished course 0, and to take course 0 you sho
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 207 :lc-lang python3
 class Solution:
     def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 207
 class Solution {
 public:
     bool canFinish(int numCourses, vector<vector<int>>& prerequisites) {

org/study_deck_02/dsa/graphs/0210-course-schedule-ii.org

@@ -58,13 +58,13 @@ Output: [0]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 210 :lc-lang python3
 class Solution:
     def findOrder(self, numCourses: int, prerequisites: List[List[int]]) -> List[int]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 210
 class Solution {
 public:
     vector<int> findOrder(int numCourses, vector<vector<int>>& prerequisites) {

org/study_deck_02/dsa/graphs/0261-graph-valid-tree.org

@@ -8,11 +8,11 @@
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 261 :lc-lang python3
 
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 261
 
 #+end_src

org/study_deck_02/dsa/graphs/0286-walls-and-gates.org

@@ -8,11 +8,11 @@
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 286 :lc-lang python3
 
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 286
 
 #+end_src

org/study_deck_02/dsa/graphs/0323-number-of-connected-components-in-an-undirected-graph.org

@@ -8,11 +8,11 @@
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 323 :lc-lang python3
 
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 323
 
 #+end_src

org/study_deck_02/dsa/graphs/0417-pacific-atlantic-water-flow.org

@@ -61,13 +61,13 @@ Explanation: The water can flow from the only cell to the Pacific and Atlantic o
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 417 :lc-lang python3
 class Solution:
     def pacificAtlantic(self, heights: List[List[int]]) -> List[List[int]]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 417
 class Solution {
 public:
     vector<vector<int>> pacificAtlantic(vector<vector<int>>& heights) {

org/study_deck_02/dsa/graphs/0684-redundant-connection.org

@@ -48,13 +48,13 @@ Output: [1,4]
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 684 :lc-lang python3
 class Solution:
     def findRedundantConnection(self, edges: List[List[int]]) -> List[int]:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 684
 class Solution {
 public:
     vector<int> findRedundantConnection(vector<vector<int>>& edges) {

org/study_deck_02/dsa/graphs/0695-max-area-of-island.org

@@ -43,13 +43,13 @@ Output: 0
 Write your approach here.
 
 ** TODO Python
-#+begin_src python
+#+begin_src python :lc-problem 695 :lc-lang python3
 class Solution:
     def maxAreaOfIsland(self, grid: List[List[int]]) -> int:
 #+end_src
 
 ** TODO C++
-#+begin_src cpp
+#+begin_src cpp :lc-problem 695
 class Solution {
 public:
     int maxAreaOfIsland(vector<vector<int>>& grid) {