#include<iostream>
using namespace std;
int board[8] = {0,0,0,0,0,0,0,0};
void print_board();
int illegal(int);
void eight_queen(int);
int main()
{
   
        eight_queen(0);

    return 1;
}


void eight_queen(int i)
{
    if (i >= 8)
        print_board();
    else
    {
        for (int j=0; j<8; j++)
        {
            board[i+1] = j;
            if ( !illegal(i+1) )
                eight_queen(i+1);
        }
    }
}



int  illegal(int n)
{
    for (int i=0; i< n-1; i++)
        for (int j=i+1; j < n; j++)
        {
            if (board[i] == board[j] ||
                abs(board[i]-board[j]) == abs(i-j) )
                return 1;
        }
    return 0;
}


void print_board()
{
    static int cnt = 1;
    printf("ANS: %d\n", cnt++);

    for (int i=0; i<8; i++)
    {
        for (int j=0; j<8; j++)
            if (j==board[i])
                printf("O");
            else
                printf(".");
        cout << endl;
    }
}

用递归做的