标签：

2
2
5 10 5 8 3 10 3 8
8 8 8 6 7 8 7 6
1
0 0 2 2 2 0 0 2

Case #1:
17
Case #2:
4

旋转卡壳，和bzoj上那题基本相同

#include<cstdio>  
#include<cstdlib>  
#include<cstring>  
#include<iostream>  
#include<algorithm>  
#include<functional>  
#include<cmath>  
using namespace std;  
#define For(i,n) for(int i=1;i<=n;i++)
#define Fork(i,k,n) for(int i=k;i<=n;i++)
#define Rep(i,n) for(int i=0;i<n;i++)
#define ForD(i,n) for(int i=n;i;i--)
#define RepD(i,n) for(int i=n;i>=0;i--)
#define Forp(x) for(int p=pre[x];p;p=next[p])
#define Forpiter(x) for(int &p=iter[x];p;p=next[p])  
#define MAXN (10000+10)  
#define INF (1000000000)  
#define eps 1e-6  
struct P  
{  
    double x,y;  
    P(){}  
    P(double _x,double _y):x(_x),y(_y){}  
    friend bool operator<(P a,P b){return (fabs(a.y-b.y)<eps)?a.x<b.x:a.y<b.y;  }  
    friend bool operator==(P a,P b){return fabs(a.x-b.x)<eps&&fabs(a.y-b.y)<eps;}  
    friend bool operator!=(P a,P b){return !(a==b);}  
      
}a[MAXN],s[MAXN],ansp[5];  
int size=0;  
double ans=INF;  
double dis2(P a,P b){return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);}  
struct V  
{  
    double x,y;  
    V(){}  
    V(double _x,double _y):x(_x),y(_y){}  
    V(P a,P b):x(b.x-a.x),y(b.y-a.y){}  
    friend double operator*(V a,V b){return a.x*b.y-a.y*b.x;}  
    friend V operator*(double a,V b){return V(a*b.x,a*b.y);}  
    friend double operator/(V a,V b){return a.x*b.x+a.y*b.y;}  
    friend P operator+(P a,V b){return P(a.x+b.x,a.y+b.y);}  
    friend P operator-(P a,V b){return P(a.x-b.x,a.y-b.y);}  
    friend V operator~(V a){return V(a.y,-a.x);}  
    double dis2(){return x*x+y*y;   }     
};  
int cmp(P A,P B)  
{  
    double tmp=V(a[1],A)*V(a[1],B);  
    if (tmp>0) return 1;  
    else if (fabs(tmp)<eps) return (-dis2(A,a[1])-dis2(B,a[1])>0);  
    return 0;  
}  
int n;  
  
int main()  
{
//	freopen("F.in","r",stdin);

	int T;
	cin>>T;
	For(kcase,T)
	{
		ans=INF;
	    scanf("%d",&n);  
	    n*=4;
	    for(int i=1;i<=n;i++) scanf("%lf%lf",&a[i].x,&a[i].y);  
	    for (int i=2;i<=n;i++) if (a[i]<a[1]) swap(a[1],a[i]);  
	    sort(a+2,a+1+n,cmp);  
	    s[1]=a[1];size=1;  
	    for (int i=2;i<=n;)  
	        if (size<2||V(s[size-1],s[size])*V(s[size],a[i])>eps) s[++size]=a[i++];  
	        else size--;  
	    s[0]=s[size];  
	      
	    int l=1,r=1,t=1;  
	    for (int i=0;i<size;i++)  
	    {  
	        while (V(s[i],s[i+1])*V(s[i],s[t+1])-V(s[i],s[i+1])*V(s[i],s[t])>-eps) t=(t+1)%size;   
	        while (V(s[i],s[i+1])/V(s[i],s[r+1])-V(s[i],s[i+1])/V(s[i],s[r])>-eps) r=(r+1)%size;   
	        if (i==0) l=r;  
	        while (V(s[i],s[i+1])/V(s[i],s[l+1])-V(s[i],s[i+1])/V(s[i],s[l])<eps) l=(l+1)%size;   
	        double Dis2=dis2(s[i],s[i+1]),wlxdis=V(s[i],s[i+1])/V(s[i],s[l]),wrxdis=V(s[i],s[i+1])/V(s[i],s[r]),hxdis=V(s[i],s[i+1])*V(s[i],s[t]);  
	        double tmp=hxdis*(wrxdis-wlxdis)/Dis2;        
	        if (tmp<0) tmp=-tmp;  
	        if (ans>tmp)  
	        {  
	            ans=tmp;  
	            ansp[0]=s[i]-(wlxdis/Dis2)*V(s[i+1],s[i]);  
	            ansp[1]=s[i]+(wrxdis/Dis2)*V(s[i],s[i+1]);  
	            ansp[2]=ansp[1]+(hxdis/Dis2)*(~V(s[i+1],s[i]));           
	            ansp[3]=ansp[0]+(hxdis/Dis2)*(~V(s[i+1],s[i]));           
	        }  
	    }  
	    int p=0;  
	    for (int i=1;i<4;i++) if (ansp[i]<ansp[p]) p=i;//p=0;  
		printf("Case #%d:\n",kcase);
	    printf("%.0lf\n",ans);    
	    
	}
    return 0;  
}  

BC 2015年百度之星程序设计大赛 - 初赛(1)(矩形面积-旋转卡壳)

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原文地址：http://blog.csdn.net/nike0good/article/details/46344431