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CombinationSumII.java
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package com.yangchd.leetcode.medium;
import java.util.*;
/**
* @author yangchd 2018/7/19.
*
* 40. Combination Sum II
*
* 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]
* ]
*
*/
public class CombinationSumII {
class Solution {
public List<List<Integer>> combinationSum2(int[] candidates, int target) {
List<List<Integer>> list = new ArrayList<List<Integer>>();
Stack<Integer> numStack = new Stack<Integer>();
Arrays.sort(candidates);
checkNum(candidates, 0, target, list, numStack);
return list;
}
private void checkNum(int[] candidates, int start, int target, List<List<Integer>> list, Stack<Integer> numStack) {
if (target < 0) {
return;
}
if (target == 0) {
list.add(new ArrayList<Integer>(numStack));
return;
}
for (int i = start; i < candidates.length; i++) {
if (i > start && candidates[i] == candidates[i - 1]) {
continue;
}
numStack.push(candidates[i]);
checkNum(candidates, i + 1, target - candidates[i], list, numStack);
numStack.pop();
}
}
}
}