【LeetCode】78.Subsets(Medium)解题报告

【LeetCode】78.Subsets(Medium)解题报告

题目地址：https://leetcode.com/problems/subsets/description/
题目描述：

  Given a set of distinct integers, nums, return all possible subsets (the power set).
  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],
  []
]

  给的集合里面也没有重复数字。模板backtracking。

Solutions:

class Solution {
    public List<List> subsets(int[] nums) {
        List<List> res = new ArrayList<>();
        List temp = new ArrayList<>();
        if(nums.length==0 || nums == null) return res;
        helper(res,temp,nums,0);
        return res;
    }
    public void helper(List<List> res,List temp,int[] nums,int index){
        //要加上new ArrayList<>()
        res.add(new ArrayList<>(temp));
        for(int i=index;i1);
            temp.remove(temp.size()-1);
        }
    }
}

Date：2018年1月3日