#include<iostream>
using namespace std;
#define N 50010
#define MAX 100000
struct Point {
	int x;
	int y;
}P[N];
int stack[N];
int top;
inline int  dirc(Point p1,Point p2,Point p3)  {
	return (p3.x-p1.x)*(p2.y-p1.y)-(p3.y-p1.y)*(p2.x-p1.x);
}
inline int range(Point p1,Point p2)  {
	return (p2.x-p1.x)*(p2.x-p1.x)+(p2.y-p1.y)*(p2.y-p1.y);
}

int comp(const void* p1,const void* p2)  {
	int d=dirc(P[0],*(Point*)p1,*(Point*)p2);
	if(d==0) return range(P[0],*(Point*)p1)-range(P[0],*(Point*)p2);
	return d;
}	
int main()  {
	int n;
	while(scanf("%d",&n)!=EOF)  {
		top=-1;
		int i,j,pos=0,max=0,min=MAX;
	for(i=0;i<n;i++)   {
		scanf("%d%d",&P[i].x,&P[i].y);
		if(P[i].y<min)  {
			pos=i;
			min=P[i].y;
		}
	}
	swap(P[0],P[pos]);
	qsort(&P[1],n-1,sizeof(Point),comp);
	stack[++top]=0;
	stack[++top]=1;
	for(i=2;i<n;i++)  {
		int d=dirc(P[stack[top-1]],P[stack[top]],P[i]);
		if(d<0)	stack[++top]=i;
		else stack[top]=i;
	}
	for(i=0;i<top;i++)
		for(j=i+1;j<=top;j++)
			if(range(P[stack[i]],P[stack[j]])>max) {
				max=range(P[stack[i]],P[stack[j]]);
			}
	printf("%d\n",max);
	}
	return 0;
}

• Re:吐血啊 WA十几次 谁能帮忙瞧一下哇 (1248) bjtu1 2009-07-18 14:21:34
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