cc65/test/ref/8q.c

/*
  !!DESCRIPTION!! solves the "8 queens" chess problem
  !!ORIGIN!!      LCC 4.1 Testsuite
  !!LICENCE!!     own, freely distributeable for non-profit. read CPYRIGHT.LCC
*/

#include <stdio.h>

int up[15], down[15], rows[8], x[8];
void queens(int c);
void print(void);

int main(void)
{
        int i;
        for (i = 0; i < 15; i++)
                up[i] = down[i] = 1;
        for (i = 0; i < 8; i++)
                rows[i] = 1;
        queens(0);
        return 0;
}

void queens(int c)
{
        int r;

        for (r = 0; r < 8; r++)
                if (rows[r] && up[r-c+7] && down[r+c]) {
                        rows[r] = up[r-c+7] = down[r+c] = 0;
                        x[c] = r;
                        if (c == 7)
                                print();
                        else
                                queens(c + 1);
                        rows[r] = up[r-c+7] = down[r+c] = 1;
                }
}

void print(void)
{
        int k;

        for (k = 0; k < 8; k++) {
                printf("%c", x[k]+'1');
                if(k<7) printf(" ");
        }
        printf("\n");
}