[leetcode]Permutations

dfs枚举

 

class Solution {
public:
    unordered_set<int> st;
    void search(vector<int> &num , vector<vector<int> > &ans ,  vector<int>& tmp , int dep ,int size) {
        if(dep >= size) {
            ans.push_back(tmp);
            return ;
        }
        
        for(int i = 0 ; i < size ; i++) {
            if (st.find(num[i]) == st.end()) {
                st.insert(num[i]);
                tmp.push_back(num[i]);
                search(num , ans , tmp ,  dep + 1 , size);
                tmp.pop_back();
                st.erase(num[i]);
            }
        }
    }
    vector<vector<int> > permute(vector<int> &num) {
        sort(num.begin() , num.end());
        st.clear();
        vector<int> tmp;
        vector<vector<int> > ans;
        search(num , ans , tmp , 0 , num.size());
        return ans;
    }
};