（fro循环）.cpp

自己收集的八皇后问题相关知识,有不少源代码,能解决八皇后问题

#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(" heh..I can't calculate that.\n");
		exit(-1);
	}
	printf("%d Queens\n",n);
	upperlim=(upperlim<<n)-1;
	test(0,0,0);
	printf("Number of solutions is %ld, %d seconds\n", sum,(int)(time(0)-tm));
}