leetcode:N-Queens 问题

一、N-QueensII

 class Solution {
 public:
     int totalNQueens(int n) {
         int total = ;
         vector<int> v(n,);
         dfs(,n,total,v);
         return total;
     }
 private:
     bool isvalide(vector<int>& v,int x){
         for(int i=;i<x;i++){
             if(v[i]==v[x] || abs(v[x]-v[i])==abs(x - i))
                 return false;
         }
         return true;
     }

     void dfs(int curr,int n,int& total,vector<int>& v){
         if(curr == n) {
             total++;
             return;
         }

         for(int i=;i<n;i++){
             v[curr] = i;
             if(isvalide(v,curr)){
                 dfs(curr+,n,total,v);
             }
         }
     }
 };

二、N-Queens

 class Solution {
 public:
     vector<vector<string>> solveNQueens(int n) {
         vector<vector<string>> result;
         vector<int> v(n,-);
         dfs(,n,v,result);
         return result;
     }
     bool isValide(vector<int>& v,int curr){
         for(int i=;i< curr;i++){
             if(v[i] == v[curr] || abs(v[curr]-v[i])==abs(curr-i))
                 return false;
         }
         return true;
     }
     void dfs(int curr,int n,vector<int>& v,
             vector<vector<string>>& result){
         if(curr == n){
             vector<string> temp;
             for(int i=;i<n;i++){
                 string s(n,'.');
                 s[v[i]] = 'Q';
                 temp.push_back(s);
             }
             result.push_back(temp);
             return;
         }
         for(int i=;i<n;i++){
             v[curr] = i;
             if(isValide(v,curr)){
                 dfs(curr+, n, v,result);
             }
         }
     }
 };