sdut1882n皇后问题

http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=1882

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#include <stdio.h>
#include <stdlib.h>
#include<math.h>
int q[21][21],flag,a[21],f = 0;
void dfs(int i, int n)
{
    int j,k,p,l,m;
    if(f == 1)
    return ;
    if(i>n)
    {
       for(l = 1 ; l <= n ; l++)
        {
            printf("%d ", a[l]);
        }
        printf("\n");
        f = 1;
    }
    else
    {
        for(j = 1 ; j <= n; j++)
        {
            flag = 0;
            for(k = 1 ; k < i ; k++)
            if(a[k] == j||(abs(k-i)==abs(a[k]-j)))
            flag = 1;
            if(flag == 0)
            {
                q[i][j] = 0;
                a[i] = j;
                dfs(i+1,n);
                q[i][j] = 1;
            }
        }
    }
}
int main()
{
    int n, i, j,p = 1,l;
    scanf("%d", &n);
    for(i = 1 ; i <= n ; i++)
    for(j = 1 ; j <= n ; j++)
    q[i][j] = 1;
    dfs(1, n);
    return 0;
}