# Combination Sum II

## Problem

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.

Notice

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.

## Example

Given candidate set [10,1,6,7,2,1,5] and target 8,

A solution set is:

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

## Code - Java

public class Solution {
/**
* @param num:    Given the candidate numbers
* @param target: Given the target number
* @return: All the combinations that sum to target
*/
public List<List<Integer>> combinationSum2(int[] num, int target) {
Set<List<Integer>> result = new HashSet<>();
Arrays.sort(num);
for (int i = 0; i < num.length; i++) {
List<Integer> buffer = new ArrayList<>();
search(result, buffer, num, target - num[i], i);
}
return new ArrayList<>(result);

}

private void search(Set<List<Integer>> result, List<Integer> buffer, int[] num, int target, int level) {
if (target < 0) return;
if (target == 0) {
}