N-Queens

The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.

Given an integer n, return all distinct solutions to the n-queens puzzle.

Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space respectively.

For example,
There exist two distinct solutions to the 4-queens puzzle:

[ [".Q..", // Solution 1 "...Q", "Q...", "..Q."], ["..Q.", // Solution 2 "Q...", "...Q", ".Q.."] ]

class Solution {
public:
    vector<vector<string> > solveNQueens(int n) 
    {
        vector<vector<string>> result;
        if(n==0) return result;
        int loc[n];
        generate(result,loc,n,0);
        return result;
    }
    void generate(vector<vector<string>>& result,int* loc,int n,int row)
    {
        if(row==n)
        {
            vector<string> v;
            for(int i=0;i<n;i++)
            {
                string s;
                for(int j=0;j<n;j++) s=s+".";
                s[loc[i]]='Q';
                v.push_back(s);
            }
            result.push_back(v);
            return;
        }
        for(int i=0;i<n;i++)
        {
            int j;
            for(j=0;j<row;j++)
                if(loc[j]==i || row-j==loc[j]-i || row-j==i-loc[j])
                    break;
            if(j==row)
            {
                loc[row]=i;
                generate(result,loc,n,row+1);
            }
        }
    }
};