leetcode [78] Subsets

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

Note: The solution set must not contain duplicate subsets.

Example:

Input: nums = [1,2,3]

Output:[

[3],

[1],

[2],

[1,2,3],

[1,3],

[2,3],

[1,2],

[]

]

题目大意：

找出的集合的所有子集，集合元素并不重复

 

解法：

C++：

class Solution {
public:
    void dfs(vector<int> nums,int index,vector<int>&tmp,vector<vector<int>>&res){
        res.push_back(tmp);
        if(index==nums.size()) return;
        for(int i=index;i<nums.size();i++){
            tmp.push_back(nums[i]);
            dfs(nums,i+1,tmp,res);
            tmp.pop_back();
        }
    }
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<int>tmp;
        vector<vector<int>>res;
        dfs(nums,0,tmp,res);
        return res;
    }
};

Python:

class Solution(object):
    def dfs(self,nums,res,tmp,index):
        res.append(tmp)
        if index==len(nums):
            return
        for i in range(index,len(nums)):
            self.dfs(nums,res,tmp+[nums[i]],i+1)
            
            
    def subsets(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        if not nums:
            return None
        res=[]
        tmp=[]
        self.dfs(nums,res,tmp,0)
        return res