poj_2187凸包，暴力解法

来源：互联网发布：windows ce6.0刷机包编辑：程序博客网时间：2024/05/22 11:52
#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>using namespace std;struct Point{    int x,y;    Point(int x=0,int y=0):x(x),y(y){}};typedef Point Vector;bool cmp(const Point &p,const Point &q){    if(p.x!=q.x) return p.x<q.x;    return p.y<q.y;}Vector operator -(Point A,Point B){return Vector(A.x-B.x,A.y-B.y);}Point p[50010],ch[50010];int Cross(Vector A,Vector B){return A.x*B.y-A.y*B.x;}int ConvexHull(Point *p,int n,Point *ch){    sort(p,p+n,cmp);    int m=0;    for(int i=0;i<n;i++){        while(m>1&&Cross(ch[m-1]-ch[m-2],p[i]-ch[m-2])<=0)m--;    ch[m++]=p[i];}    int k=m;    for(int i=n-2;i>=0;i--)    {        while(m>k&&Cross(ch[m-1]-ch[m-2],p[i]-ch[m-2])<=0)m--;        ch[m++]=p[i];    }    if(n>1)        m--;    return m;}int Dot(Vector A,Vector B){return A.x*B.x+A.y*B.y;}int Length(Vector A){return Dot(A,A);}int main(){    int n;    while(scanf("%d",&n)!=EOF)    {       for(int i=0;i<n;i++)            scanf("%d%d",&p[i].x,&p[i].y);       int x=ConvexHull(p,n,ch);        int ans=0;        for(int i=0;i<x-1;i++)            for(int j=i+1;j<x;j++)            if(Length(ch[i]-ch[j])>ans)                ans=Length(ch[i]-ch[j]);            printf("%d\n",ans);    }    return 0;}
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