47. 全排列 II(LeetCode中等)(DFS元素重复板子)

47. 全排列 II
对于相同的数,只用第一个没有用过的

class Solution {
public:
    vector<vector<int>> ans;
    vector<int> path;
    vector<bool> st;

    vector<vector<int>> permuteUnique(vector<int>& nums) {
        int n = nums.size();
        path = vector<int>(n);
        st = vector<bool>(n);
        sort(nums.begin(), nums.end());
        dfs(nums, 0);

        return ans;
    }

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