# Combination Sum

39. Combination Sum

Given a set of candidate numbers (C) (without duplicates) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:
1. All numbers (including target) will be positive integers.
2. The solution set must not contain duplicate combinations.

For example, given candidate set [2, 3, 6, 7] and target 7,
A solution set is:

``````[
[7],
[2, 2, 3]
]
``````
``````public class Solution {
public List<List<Integer>> combinationSum(int[] candidates, int target) {
List<List<Integer>> result = new ArrayList<>();
if (candidates == null || candidates.length == 0) {
return result;
}

Arrays.sort(candidates);
combinationSumHelper(candidates, target, result, new ArrayList<>(), 0);

return result;
}

void combinationSumHelper(int[] candidates, int target, List<List<Integer>> result,
List<Integer> list, int start) {
if (target < 0) {
return;
}
if (target == 0) {
return;
}

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