46 全排列

https://leetcode.cn/leetbook/read/top-interview-questions-medium/xvqup5/

cost: 23m5s

class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int>> res;
        list<int> list;
        this->walk(res, nums, 0, list);
        return res;
    }

private:
    void walk(vector<vector<int>>& res, vector<int>& nums, int k,
              list<int>& list) {
        if (k == nums.size()) {
            res.emplace_back(list.begin(), list.end());
            return;
        }
        vector<int> tmp(list.begin(), list.end());
        for (const int v : tmp) {
            auto it = std::find(list.begin(), list.end(), v);
            list.insert(it, nums[k]);
            this->walk(res, nums, k + 1, list);
            list.remove(nums[k]);
        }
        list.push_back(nums[k]);
        this->walk(res, nums, k + 1, list);
        list.pop_back();
    }
};