N-Queens

class Solution {
private:
    vector<vector<string>> res;
public:
    bool isLegal(vector<string> &temp, int row, int col)
    {
         //列
        for(int i = 0; i < row; i++)
            if(temp[i][col] == ‘Q‘)return false;
        //右对角线
        for(int i = row-1, j=col-1; i >= 0 && j >= 0; i--,j--)
            if(temp[i][j] == ‘Q‘)return false;
        //左对角线
        for(int i = row-1, j=col+1; i >= 0 && j < temp.size(); i--,j++)
            if(temp[i][j] == ‘Q‘)return false;
        return true;
     }
   /* bool isLegal(vector<string> &temp,int H,int W)
    {
        for(int j=0;j<H;j++)
            for(int i=0;i<=W;i++)
            {
                if(temp[j][i]==‘Q‘&&(abs(j-H)==abs(i-W)||i==W))
                   return false;
            }
        return true;
    }*/
    void procedure(vector<string> &temp,int rows)
    {
        if(rows==temp.size())
        {
            res.push_back(temp);
            return;
        }
        for(int cols=0;cols<temp.size();cols++)
        {  if(isLegal(temp,rows,cols))
            {
              temp[rows][cols]=‘Q‘;
              procedure(temp,rows+1);
              temp[rows][cols]=‘.‘;
            }
        }
        return ;
    }
    vector<vector<string> > solveNQueens(int n) {
        if(n==1)
        {   
            vector<string> t1(1,"Q");
            vector<vector<string>> res1(1,t1);
            return res1;
        }
        if(n<4)
        {
           vector<vector<string>> res2;
           return res2;
        }
       vector<string> temp(n,string(n,‘.‘));
       procedure(temp,0);
       return res;       
    }
   
};