solve: 0217 Contains Duplicate (C++ set approach)

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

@@ -1,5 +1,5 @@
 #+PROPERTY: STUDY_DECK_02
-* TODO 0217. Contains Duplicate :easy:
+* DONE 0217. Contains Duplicate :easy:
 :PROPERTIES:
 :NEETCODE: [[file:../../roadmap.org::*0217. Contains Duplicate][0217. Contains Duplicate]]
 :END:
@@ -38,10 +38,10 @@ All elements are distinct.
 
  - ~-10^{9} <= nums[i] <= 10^{9}~
 
-** TODO Approach
+** DONE Approach
 Write your approach here.
 
-** TODO Python
+** DONE Python
 #+begin_src python
 class Solution:
     def containsDuplicate(self, nums: List[int]) -> bool:
@@ -53,12 +53,21 @@ class Solution:
         return False
 #+end_src
 
-** TODO C++
+** DONE C++
 #+begin_src cpp
+#include <vector>
+#include <set>
 class Solution {
 public:
-    bool containsDuplicate(vector<int>& nums) {
-        
+  bool containsDuplicate(std::vector<int>& nums) {
+    std::set<int> s;
+    for (int x: nums) {
+      if (s.contains(x)) {
+        return true;
+      }
+      s.insert(x);
     }
+    return false;
+  }
 };
 #+end_src