# Combination Sum Leetcode Solution

In this post, we are going to solve the Combination Sum Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

## Problem

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:

```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.
```

Example 2:

```Input: candidates = [2,3,5], target = 8
Output: [[2,2,2,2],[2,3,3],[3,5]]
```

Example 3:

```Input: candidates = [2], target = 1
Output: []
```

Constraints:

• `1 <= candidates.length <= 30`
• `2 <= candidates[i] <= 40`
• All elements of `candidates` are distinct.
• `1 <= target <= 500`

Now, lets see the leetcode solution of Combination Sum Leetcode Solution.

### Combination Sum Leetcode Solution in Python

```class Solution:
def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
ans = []

def dfs(s: int, target: int, path: List[int]) -> None:
if target < 0:
return
if target == 0:
ans.append(path.clone())
return

for i in range(s, len(candidates)):
path.append(candidates[i])
dfs(i, target - candidates[i], path)
path.pop()

candidates.sort()
dfs(0, target, [])
return ans
```

### Combination SumLeetcode Solutionin CPP

```class Solution {
public:
vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
vector<vector<int>> ans;

sort(begin(candidates), end(candidates));
dfs(candidates, 0, target, {}, ans);
return ans;
}

private:
void dfs(const vector<int>& A, int s, int target, vector<int>&& path,
vector<vector<int>>& ans) {
if (target < 0)
return;
if (target == 0) {
ans.push_back(path);
return;
}

for (int i = s; i < A.size(); ++i) {
path.push_back(A[i]);
dfs(A, i, target - A[i], move(path), ans);
path.pop_back();
}
}
};
```

### Combination Sum Leetcode Solution in Java

```class Solution {
public List<List<Integer>> combinationSum(int[] candidates, int target) {
List<List<Integer>> ans = new ArrayList<>();

Arrays.sort(candidates);
dfs(0, candidates, target, new ArrayList<>(), ans);
return ans;
}

private void dfs(int s, int[] candidates, int target, List<Integer> path,
List<List<Integer>> ans) {
if (target < 0)
return;
if (target == 0) {
return;
}

for (int i = s; i < candidates.length; ++i) {