Leetcode 46 Permutation Leetcode 78 Subsets

Permutation
题意
https://leetcode.com/problems/permutations/description/

返回[1,2,3]的全排列

首先既然是全排列对吧，我需要统计这个tmp数组里的元素个数是不是究竟等于3，然后iterate所有的数字对吧

class Solution {
public:
    vector<vector<int>> arr;
    
    vector<vector<int>> permute(vector<int>& nums) {
        vector<int> tmp;
        vector<bool> vis(nums.size(), false);
        dfs(nums, tmp, vis);
        return arr;
    }
    void dfs(vector<int>& nums, vector<int>& tmp, vector<bool>& vis){
        if (tmp.size() == nums.size()) {
            arr.push_back(tmp);
        }
        for(int i = 0; i < nums.size(); i++) {
            if (!vis[i]) {
                tmp.push_back(nums[i]);
                vis[i] = true;
                dfs(nums,tmp, vis);
                tmp.pop_back();
                vis[i] = false;
            }
        }
    }
};

Subsets
题意，返回[1,2,3]所有的组合

我在dfs中每次某个位置的元素进行选或者不选的操作

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