mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
87 lines
1.7 KiB
C++
87 lines
1.7 KiB
C++
#include<stdio.h>
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#include<math.h>
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#include<algorithm>
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using namespace std;
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struct aa
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{
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int x,y;
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}a1[105],a2[105];
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double maxx(double x,double y)
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{
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return x>y?x:y;
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}
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double abss(double x)
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{
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return x>0?x:-x;
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}
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double x_y(aa a,aa b)
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{
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return sqrt((a.x-b.x)*(a.x-b.x)*1.0+(a.y-b.y)*(a.y-b.y)*1.0);
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}
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double sss(aa A,aa B,aa C)
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{
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return (B.x - A.x)*(C.y - B.y) - (C.x - B.x)*(B.y - A.y);
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}
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bool camp(aa a,aa b)
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{
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return a.y<b.y||a.y==b.y&&a.x<b.x;
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}
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bool fx(aa A,aa B,aa C)
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{
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return (A.x - B.x)*(C.y - B.y) > (C.x - B.x)*(A.y - B.y);
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}
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int main ()
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{
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int i,j,k,n,t,tt;
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double a,b,c,r,s,maxr;
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while(~scanf("%d",&n)&&n)
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{
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for(i=1;i<=n;i++)
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scanf("%d%d",&a1[i].x,&a1[i].y);
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if(n==1)
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{
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printf("0.50\n");
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continue;
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}
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if(n==2)
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{
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printf("%.2f\n",x_y(a1[1],a1[2])/2+0.5);
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continue;
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}
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sort(a1+1,a1+n+1,camp);
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a2[1]=a1[1];
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a2[2]=a1[2];
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for(t=2,i=3;i<=n;i++)
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{
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while(t!=1&&!fx(a2[t],a2[t-1],a1[i]))
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t--;
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a2[++t]=a1[i];
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}
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a2[t+1]=a1[n-1];
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for(tt=t+1,i=n-2;i>=1;i--)
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{
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while(t!=tt&&!fx(a2[tt],a2[tt-1],a1[i]))
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tt--;
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a2[++tt]=a1[i];
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}
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for(maxr=0,i=1;i<tt;i++)
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for(j=i+1;j<tt;j++)
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for(k=j+1;k<tt;k++)
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{
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a=x_y(a2[i],a2[j]);
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b=x_y(a2[i],a2[k]);
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c=x_y(a2[j],a2[k]);
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if(a*a+b*b<c*c||a*a+c*c<b*b||b*b+c*c<a*a)
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r=max(max(a,b),c)/2.0;
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else
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{
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s=abss(sss(a2[i],a2[j],a2[k]))/2.0;
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r=a*b*c/4.0/s;
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}
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maxr=max(r,maxr);
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}
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printf("%.2f\n",maxr+0.5);
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}
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return 0;
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}
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