# Combination Sum Leetcode Solution

#### ByBrokenprogrammers

Dec 19, 2022

In this post, you will know how to solve the Combination Sum Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

One more thing to add, don’t directly look for the solutions, first try to solve the problems of Leetcode by yourself. If you find any difficulty after trying several times, then you can look for solutions.

## 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`

### Combination Sum Leetcode Solutions 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 Solutionsin 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 Solutions 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) {
dfs(i, candidates, target - candidates[i], path, ans);
path.remove(path.size() - 1);
}
}
}
```

Note: This problem Combination Sum is generated by Leetcode but the solution is provided by BrokenProgrammers. This tutorial is only for Educational and Learning purposes.