40. 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. Elements in a combination (a1, a2, ... , ak) must be in non-descending order. (ie, a1 <= a2 <= ... <= ak). 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] public class Solution { public List> combinationSum2(int[] a, int target) { List> res = new ArrayList>(); List l = new ArrayList(); Arrays.sort(a); solve(a, target, 0, 0, l, res); return res; } public void solve(int[] a, int target, int sum, int i, List l, List> res) { if(sum == target) { res.add(new ArrayList(l)); return; } if(sum>target) return; for(int j=i; ji && a[j]==a[j-1]) { continue; } l.add(a[j]); solve(a, target, sum+a[j], j+1, l, res); l.remove(l.size()-1); } return; } }