题目要求

Given a set of distinct integers, nums, return all possible subsets.Note: The solution set must not contain duplicate subsets.For example,If nums = [1,2,3], a solution is:[  [3],  [1],  [2],  [1,2,3],  [1,3],  [2,3],  [1,2],  []]

类似的题目有：

leetcode60 Permutation Sequence 可以参考leetcode77 Combinations 可以参考

思路一：递归

还是利用递归的方式，在前一种情况的基础上遍历下一轮的组合情况。

public List
    
     
      > subsets(int[] nums) {        List
      
       
        > result = new ArrayList
        
         
          >(); result.add(new ArrayList
          
           ()); subsets(result, nums, 0, new ArrayList
           
            ()); return result; } public void subsets(List
            
             
              > result, int[] nums, int startIndex, List
              
                currentList){ if(startIndex == nums.length){ return; } while(startIndex
               
                (currentList)); subsets(result, nums, startIndex, currentList); currentList.remove(currentList.size()-1); } }
               
              
             
            
           
          
         
        
       
      
     
    

思路2：排序后循环

起始subset集为：[]

添加S0后为：[], [S0]添加S1后为：[], [S0], [S1], [S0, S1]添加S2后为：[], [S0], [S1], [S0, S1], [S2], [S0, S2], [S1, S2], [S0, S1, S2]

public List
    
     
      > subsets(int[] S) {    List
      
       
        > res = new ArrayList<>();    res.add(new ArrayList
        
         ());        for(int i : S) {        List
         
          
           > tmp = new ArrayList<>(); for(List
           
             sub : res) { List
            
              a = new ArrayList<>(sub); a.add(i); tmp.add(a); } res.addAll(tmp); } return res;}
            
           
          
         
        
       
      
     
    

想要了解更多开发技术，面试教程以及互联网公司内推，欢迎关注我的微信公众号！将会不定期的发放福利哦~