Combination Sum II

Given a collection of candidate numbers ($C$) and a target number ($T$), find all unique combinations in $C$ where the candidate numbers sums to $T$.

Each number in $C$ may only be used once in the combination.

Note:

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

For example, given candidate set [10, 1, 2, 7, 6, 1, 5] and target 8, A solution set is:

[
  [1, 7],
  [1, 2, 5],
  [2, 6],
  [1, 1, 6]
]

Note:

combinationSum2(ans, candidates, target-candidates[i], i+1, list); use i+1 to control duplicate selection.

if(i>start && candidates[i]==candidates[i-1]) continue; use i>start instead of i>0 to include the case when candidates has duplicate numbers.

Solution:

public class Solution {
    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        Arrays.sort(candidates);
        List<List<Integer>> ans = new ArrayList<>();
        combinationSum2(ans, candidates, target, 0, new ArrayList<Integer>());
        return ans;
    }
    public void combinationSum2(List<List<Integer>> ans, int[] candidates, int target, int start, List<Integer> list){
        if(target==0){
            ans.add(new ArrayList<>(list));
            return;
        }
        for(int i=start; i<candidates.length; i++){
            if(i>start && candidates[i]==candidates[i-1]) continue;
            if(target-candidates[i]<0) break;
            list.add(candidates[i]);
            combinationSum2(ans, candidates, target-candidates[i], i+1, list);
            list.remove(list.size()-1);
        }
    }
}