leetcode-master/problems/0046.全排列.md

题目地址

https://leetcode-cn.com/problems/permutations/

思路

先写逻辑，再确认参数，先把for循环写出来，在写 结束语句，在写 函数参数。

这道题目树形结构还不太一样

解法

class Solution {
public:
    vector<vector<int>> result;
    void backtracking (vector<int>& nums, vector<int>& vec, vector<bool>& used) {
        // 此时说明找到了一组
        if (vec.size() == nums.size()) {
            result.push_back(vec);
            return;
        }

        for (int i = 0; i < nums.size(); i++) {
            if (used[i] == false) {
                used[i] = true;
                vec.push_back(nums[i]);
                backtracking(nums, vec, used);
                vec.pop_back();
                used[i] = false;
            }
        }
    }
    vector<vector<int>> permute(vector<int>& nums) {
        vector<bool> used(nums.size(), false);
        vector<int> vec;
        backtracking(nums, vec, used);
        return result;
    }
};

这是一个思路： class Solution { public: vector<vector> res; vector<vector> permute(vector& nums) { solve(nums, 0); return res; } void solve(vector &nums, int idx) { if(idx == nums.size()-1 || nums.size() == 0){ res.push_back(nums); return; } for(int i = idx; i < nums.size(); i++){ swap(nums[idx], nums[i]); solve(nums, idx+1); swap(nums[idx], nums[i]); } } };