#include <stdio.h>
#include <stdlib.h>
#include <time.h>
long sum = 0, upperlim = 1;
void test(long row, long ld, long rd)
{
if (row != upperlim)
{
long pos = upperlim & ~(row | ld | rd);
while (pos)
{
long p = pos & -pos;
pos -= p;
test(row + p, (ld + p) << 1, (rd + p) >> 1);
}
} else
sum++;
}
int main(int argc, char *argv[])
{
time_t tm;
int n = 16;
if (argc != 1)
n = atoi(argv[1]);
tm = time(0);
if ((n < 1) || (n > 32))
{
printf(" 只能计算1-32之间\n");
exit(-1);
}
printf("%d 皇后\n", n);
upperlim = (upperlim << n) - 1;
test(0, 0, 0);
printf("共有%ld种排列, 计算时间%d秒 \n", sum, (int) (time(0) - tm));
}
