LeetCode Permutations

class Solution {

private:

    vector<vector<int> > result;

public:

    vector<vector<int> > permute(vector<int> &num) {

        result.clear();

        dfs(num, 0);

        return result;

    }

    

    void dfs(vector<int>& num, int idx) {

        int tmp;

        int len = num.size();

        if (len == idx + 1) {

            result.push_back(num);

            return;

        }

        for (int i=idx; i<len; i++) {

            tmp = num[idx];

            num[idx] = num[i];

            num[i] = tmp;

            dfs(num, idx + 1);

            tmp = num[idx];

            num[idx] = num[i];

            num[i] = tmp;

        }

    }

};

重复的情况竟然可以，又水了一发