poj3301 Texas Trip【三分算法】

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>
#include <stack>
#include <queue>
#include <iostream>
#include <string>
#include <algorithm>
#define eps 1e-9


using namespace std;

int tg, n;
int x[1000], y[1000];

double calc(double d)
{
	int i, j;
	double dis1,dis2,dis;
	dis=0.0;

	for(i=1; i<n; i++)
	{
		for(j=i+1; j<=n; j++)
		{
			dis1=fabs( cos(d)*(y[i]-y[j])-sin(d)*(x[i]-x[j]) );
			dis2=fabs( sin(d)*(y[i]-y[j])+cos(d)*(x[i]-x[j]) );
			if(dis < dis1 ) dis = dis1;
			if(dis < dis2 ) dis = dis2;
		}
	}
	return (dis*dis);
}

int main()
{
    double ll, rr, mid, midmid;
	double s1, s2;

	cin>>tg;
	while(tg--)
	{
		cin>>n;
		for(int i=1; i<=n; i++){
			cin>>x[i]>>y[i];
		}

		ll=0.0; rr=acos(-1.0); //rr=180.0 确定好区间
		while( rr-ll>=eps )
		{
			mid = (ll+rr)/2; midmid=(rr+mid)/2;

			s1=calc(mid);
			s2=calc(midmid);
			if(s1<s2){
				rr=midmid;
			}else
			{
				ll=mid;
			}
		}
		printf("%0.2lf\n", s1<s2?s1:s2);
	}
    return 0;
}