LeetCode : Combination Sum II [java]

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] 

思路：回溯算法，注意跳过相同元素。

import java.util.ArrayList;import java.util.Arrays;import java.util.List;public class Solution {public List<List<Integer>> combinationSum2(int[] candidates, int target) {List<List<Integer>> result = new ArrayList<List<Integer>>();List<Integer> current = new ArrayList<Integer>();Arrays.sort(candidates);solve(candidates, target, 0, current, result);return result;}public void solve(int[] candidates, int target, int index, List<Integer> current, List<List<Integer>> result) {if (target == 0) {List<Integer> tmp = new ArrayList<Integer>(current);result.add(tmp);return;}for (int i = index; i < candidates.length; i++) {if (target < candidates[i]) {return;}current.add(candidates[i]);solve(candidates, target - candidates[i], i + 1, current, result);current.remove(current.size() - 1);while(i<(candidates.length-1)&&candidates[i]==candidates[i+1]){                i++;            }}}}