题目地址：

题目分析：采用递归方式，先将数组排序，依次遍历数组中元素，如果target比第i个元素大则加入到结果集中，如果比第i个元素小返回；如果target为0，将组合加入到返回值中。

题目解答：

import java.util.ArrayList;import java.util.Arrays;public class Solution {    public ArrayList
     
      
       > combinationSum(int[] candidates, int target) {        ArrayList
       
         curr = new ArrayList
        
         ();        ArrayList
         
          
           > ret = new ArrayList
           
            
             >(); if(candidates == null || candidates.length == 0 || target == 0){ return ret; } Arrays.sort(candidates); combinationSum(candidates,0,target,curr,ret); return ret; } public void combinationSum(int[] candidates,int start,int target,ArrayList
             
               curr,ArrayList
              
               
                > ret){ if(target == 0){ ArrayList
                
                  temp = new ArrayList
                 
                  (curr); ret.add(temp); return; } for(int i = start;i