为啥只能倒序？

for(int j=1;j<=tot/2;j++)
{
	for(int k=1;k<=tot/2;k++)
	{
		//if(f[j][k]) printf("*");
		if(f[j][k]&&san(j,k,tot-j-k))
		{
			double half=tot*1.0/2;
			double ans=sqrt(half*(half-j)*(half-k)*(half-(tot-j-k)));
			maxans=max(maxans,ans);
		}
	}
}