POJ 2187

来源：互联网发布：热血虎卫源码编辑：程序博客网时间：2024/06/05 05:51

求最远点对距离的平方。

#include<string.h>#include<cstdio>#include<cstdlib>#include<iostream>#include<vector> #include<set>#include<cmath>#include<algorithm>using namespace std;const int maxn=50010;const int eps=1e-10;double add(double a,double b){if(abs(a + b)<eps*(abs(a)+abs(b)))return 0;return a+b;}struct P{double x,y;P(){}P(double x,double y):x(x),y(y){}P operator + (P p){return P(add(x,p.x),add(y,p.y));}P operator - (P p){return P(add(x,-p.x),add(y,-p.y));}P operator * (double d){return P(x*d,y*d);}double dot(P p){return add(x*p.x,y*p.y);}double det(P p){return add(x*p.y,-y*p.x);}};bool cmp_x(const P& p,const P& q){if(p.x!=q.x)return p.x<q.x;return p.y<q.y;}vector<P>convex_hull(P *ps,int n){sort(ps,ps+n,cmp_x);int k=0;vector<P>qs(n*2);for(int i=0;i<n;i++){while(k>1&&(qs[k-1]-qs[k-2]).det(ps[i]-qs[k-1])<=0)k--;qs[k++]=ps[i];}for(int i=n-2,t=k;i>=0;i--){while(k>t&&(qs[k-1]-qs[k-2]).det(ps[i]-qs[k-1])<=0)k--;qs[k++]=ps[i];}qs.resize(k-1);return qs;}double dist(P p,P q){return (p-q).dot(p-q);}int N;P ps[maxn];void solve(){vector<P>qs=convex_hull(ps,N);int n=qs.size();if(n==2){printf("%.0f\n",dist(qs[0],qs[1]));return;}int i=0,j=0;for(int k=0;k<n;k++){if(!cmp_x(qs[i],qs[k]))i=k;if(cmp_x(qs[j],qs[k]))j=k;}double res=0;int si=i,sj=j;while(i!=sj||j!=si){res=max(res,dist(qs[i],qs[j]));if((qs[(i+1)%n]-qs[i]).det(qs[(j+1)%n]-qs[j])<0){i=(i+1)%n;}else{j=(j+1)%n;}}printf("%.0f\n",res);}int main(){scanf("%d",&N);for(int i=0;i<N;i++)scanf("%lf%lf",&ps[i].x,&ps[i].y);solve();return 0;}

#include<string.h>#include<cstdio>#include<cstdlib>#include<iostream>#include<vector> #include<set>#include<cmath>#include<algorithm>using namespace std;const int maxn=50010;const int eps=1e-10;double add(double a,double b){if(abs(a + b)<eps*(abs(a)+abs(b)))return 0;return a+b;}struct P{double x,y;P(){}P(double x,double y):x(x),y(y){}P operator + (P p){return P(add(x,p.x),add(y,p.y));}P operator - (P p){return P(add(x,-p.x),add(y,-p.y));}P operator * (double d){return P(x*d,y*d);}double dot(P p){return add(x*p.x,y*p.y);}double det(P p){return add(x*p.y,-y*p.x);}};bool cmp_x(const P& p,const P& q){if(p.x!=q.x)return p.x<q.x;return p.y<q.y;}vector<P>convex_hull(P *ps,int n){sort(ps,ps+n,cmp_x);int k=0;vector<P>qs(n*2);for(int i=0;i<n;i++){while(k>1&&(qs[k-1]-qs[k-2]).det(ps[i]-qs[k-1])<=0)k--;qs[k++]=ps[i];}for(int i=n-2,t=k;i>=0;i--){while(k>t&&(qs[k-1]-qs[k-2]).det(ps[i]-qs[k-1])<=0)k--;qs[k++]=ps[i];}qs.resize(k-1);return qs;}double dist(P p,P q){return (p-q).dot(p-q);}int N;P ps[maxn];void solve(){vector<P>qs=convex_hull(ps,N);double res=0;for(int i=0;i<qs.size();i++){for(int j=0;j<i;j++){res=max(res,dist(qs[i],qs[j]));}}printf("%.0f\n",res);}int main(){scanf("%d",&N);for(int i=0;i<N;i++)scanf("%lf%lf",&ps[i].x,&ps[i].y);solve();return 0;}

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