# 40.Combination-Sum-II

## ้ข็ฎๅฐๅ

https://leetcode.com/problems/combination-sum-ii/

## ้ข็ฎๆ่ฟฐ

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

Each number in candidates 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.

Example 1:
Input: candidates = [10,1,2,7,6,1,5], target = 8,
A solution set is:
[
[1, 7],
[1, 2, 5],
[2, 6],
[1, 1, 6]
]
Example 2:

Input: candidates = [2,5,2,1,2], target = 5,
A solution set is:
[
[1,2,2],
[5]
]``````

## ไปฃ็ 

### Approach #1 Sort + Backtrace

`i != startIndex && candidates[i] == candidates[i - 1]` ๅป้

``````class Solution {
public List<List<Integer>> combinationSum2(int[] candidates, int target) {
List<List<Integer>> results = new ArrayList<>();
if (candidates == null || candidates.length == 0) {
return results;
}

Arrays.sort(candidates);
List<Integer> combination = new ArrayList<Integer>();
dfs(candidates, 0, combination, target, results);

return results;
}

private void dfs(int[] candidates, int startIndex, List<Integer> combination, int target, List<List<Integer>> results) {
if (target == 0) {
return;
}

for (int i = startIndex; i < candidates.length; i++) {
// IMPORTANT ๅป้
if (i != startIndex && candidates[i] == candidates[i - 1]) {
continue;
}
if (target < candidates[i]) {
break;
}