poj1569 Myacm Triangles
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<algorithm>
using namespace std;
struct point
{
double x;
double y;
}p[20];
struct T
{
int xx;//
int yy;//
int zz;//
double mianji;//
}res;
bool cmp(int a,int b)
{
return a<b;
}
point operator-(const point &a,const point &b)
{
point temp;
temp.x=a.x-b.x;
temp.y=a.y-b.y;
return temp;
}
double operator*(const point &a,const point &b)
{
return fabs(a.x*b.y-b.x*a.y);
}
double cal(point a,point b,point c)
{
point m=b-a;
point n=c-a;
return m*n/2;
}
double cal2(point a,point b,point c,point d)
{
point m=c-d;
point n=a-d;
point h=b-d;
return m*n/2+m*h/2+n*h/2;
}
int main()
{
int n;
while(scanf("%d",&n),n)
{
res.xx=-1;
res.yy=-1;
res.zz=-1;
res.mianji=0;
getchar();
int i,j,k,l;
char ch;
for(i=0;i<n;i++)
{
scanf("%c",&ch);
scanf("%lf %lf",&p[i].x,&p[i].y);
getchar();
}
double mianji1,mianji2;
for(i=0;i<n;i++)
{
for(j=i+1;j<n;j++)
{
for(k=j+1;k<n;k++)
{
//由p[i],p[j],p[k]组成的三角形
mianji1=cal(p[i],p[j],p[k]);
bool flag=true;
for(l=0;l<n;l++)
{
if(l==i||l==j||l==k)
{
continue;
}
mianji2=cal2(p[i],p[j],p[k],p[l]);
if(mianji1==mianji2)
{
flag=false;
break;
}
}
if(flag)//三角形合法
{
if(mianji1>res.mianji)
{
res.xx=i;
res.yy=j;
res.zz=k;
res.mianji=mianji1;
}
}
}
}
}
int h[3];
h[0]=res.xx;
h[1]=res.yy;
h[2]=res.zz;
sort(h,h+3,cmp);
printf("%c%c%c\n",h[0]+'A',h[1]+'A',h[2]+'A');
}
return 0;
}
//188K 0MS