[leetcode] 78. Subsets

这是一个典型的深度优先搜索问题

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

　　

#include "stdafx.h"
#include "vector"
#include "iostream"
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
	vector<int> vct;
	vector<vector<int>> cap;
	cap.push_back(vct);
	cap.push_back(vct);
	cout<<cap.size()<<endl;//此时输出为2，即使是空的容器，也占用一个位置
	return 0;
}