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

#+ANKI_DECK: study_deck_02
* TODO 0039. Combination Sum :medium:
:PROPERTIES:
:NEETCODE: [[file:../../roadmap.org::*0039. Combination Sum][0039. Combination Sum]]
:END:

Given an array of *distinct* integers ~candidates~ and a target integer ~target~, return /a list of all *unique combinations* of /~candidates~/ where the chosen numbers sum to /~target~/./ You may return the combinations in *any order*.

The *same* number may be chosen from ~candidates~ an *unlimited number of times*. Two combinations are unique if the frequency of at least one of the chosen numbers is different.

The test cases are generated such that the number of unique combinations that sum up to ~target~ is less than ~150~ combinations for the given input.

*Example 1:*


#+begin_src
Input: candidates = [2,3,6,7], target = 7
Output: [[2,2,3],[7]]
Explanation:
2 and 3 are candidates, and 2 + 2 + 3 = 7. Note that 2 can be used multiple times.
7 is a candidate, and 7 = 7.
These are the only two combinations.
#+end_src


*Example 2:*


#+begin_src
Input: candidates = [2,3,5], target = 8
Output: [[2,2,2,2],[2,3,3],[3,5]]
#+end_src


*Example 3:*


#+begin_src
Input: candidates = [2], target = 1
Output: []
#+end_src


*Constraints:*

 - ~1 <= candidates.length <= 30~

 - ~2 <= candidates[i] <= 40~

 - All elements of ~candidates~ are *distinct*.

 - ~1 <= target <= 40~

** TODO Approach
Write your approach here.

** TODO 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 :lc-problem 39
class Solution {
public:
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        
    }
};
#+end_src