> // CS algorithm
> 
> #include <stdio.h>
> 
> #define SET_BIT(x,y) x|=(1<<y)
> 
> struct rect
> {
>   int xleft,ytop;
>   int xright,ybottom;
> };
> 
> int __inline__ sign(int x)
> {
>   return x==0?0:(x<0?-1:1);
> }
> 
> int get_code(int x,int y,struct rect r)
> {
>   int code=0;
>   if (x<r.xleft) SET_BIT(code,0);
>   else if (x>r.xright) SET_BIT(code,1);
>   if (y>r.ytop) SET_BIT(code,3);
>   else if (y<r.ybottom) SET_BIT(code,2);
>   return code;
> }
> 
> int main()
> {
>   int n;
>   int i;
>   int x1,y1,x2,y2;
>   struct rect r;
>   int code1,code2;
>   int s1,s2,s3,s4;
> 
>   scanf("%d",&n);
>   for (i=0;i<n;++i) {
>     scanf("%d %d %d %d",&x1,&y1,&x2,&y2);
>     scanf("%d %d %d %d",&r.xleft,&r.ytop,&r.xright,&r.ybottom);

>     if (x1==x2 && y1==y2) {
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 线段退化为一个点后，难道就不判断点是否在矩形内部
>       printf("T\n");
>       continue;
>     }


>     if (r.xleft>r.xright) {
>       r.xleft^=r.xright;r.xright^=r.xleft;r.xleft^=r.xright;
>     }
>     if (r.ytop<r.ybottom) {
>       r.ytop^=r.ybottom;r.ybottom^=r.ytop;r.ytop^=r.ybottom;
>     }
>     code1=get_code(x1,y1,r);
>     code2=get_code(x2,y2,r);
>     if (code1&code2)
>       printf("F\n");
>     else {
>       x2-=x1;r.xleft-=x1;r.xright-=x1;
>       y2-=y1;r.ytop-=y1;r.ybottom-=y1;
>       x1=y1=0;
>       s1=sign(r.ytop*x2-r.xleft*y2);
>       s2=sign(r.ytop*x2-r.xright*y2);
>       s3=sign(r.ybottom*x2-r.xleft*y2);
>       s4=sign(r.ybottom*x2-r.xright*y2);
>       if (s1==s2 && s2==s3 && s3==s4 && s1!=0)
> 	printf("F\n");
>       else
> 	printf("T\n");
>     }
>   }
> 
>   return 0;
> }
>   

• Re:你的线段退化为点后，难道就不判断点是否在矩形内部。。 (120) richardxx 2007-01-02 02:37:13