题解 | 有重复项数字的全排列

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param num int整型vector 
     * @return int整型vector<vector<>>
     */
    vector<vector<int>> ans;
    vector<int> path;
    vector<bool> st;

    vector<vector<int> > permuteUnique(vector<int>& num) {
        sort(num.begin(), num.end());
        path = vector<int> (num.size());
        st = vector<bool> (num.size());
        dfs(num, 0);
        return ans;
    }

    void dfs(vector<int>& num, int u) {
        if (u == num.size()) ans.push_back(path);
        for (int i = 0; i < num.size(); i++) {
            if (!st[i]) {
                if (i && num[i - 1] == num[i] && st[i - 1]) continue;
                path[u] = num[i];
                st[i] = true;
                dfs(num, u + 1);
                st[i] = false;
            }
        }
    }
};