leetcode------Combination Sum II

标题：	Combination Sum II
通过率：	25.1%
难度：	中等

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] 

 

与第一个版本不同的是set中的元素不能重复使用，那么递归时起始位置就要+1操作了代码如下：

public class Solution {
    public ArrayList<ArrayList<Integer>> combinationSum2(int[] num, int target) {
        ArrayList<ArrayList<Integer>> res=new ArrayList<ArrayList<Integer>>();
        ArrayList<Integer> tmp=new ArrayList<Integer>();
        Arrays.sort(num);
        dfs(num,target,0,res,tmp);
        return res;
    }
    public void dfs(int[] num, int target,int start,ArrayList<ArrayList<Integer>> res,ArrayList<Integer> tmp){
        if(target<0)return;
        if(target==0 && !res.contains(tmp)){
            res.add(new ArrayList<Integer>(tmp));
            return ;
        }
        for(int i=start;i<num.length;i++){
            tmp.add(num[i]);
            dfs(num,target-num[i],i+1,res,tmp);
            tmp.remove(tmp.size()-1);
        }
    }
}