厦门大学 ACM 1437 三分

链接http://acm.xmu.edu.cn/JudgeOnline/problem.php?id=1437

#include<iostream>
#include<algorithm>
#include<stdio.h>
#include<cstring>
#include<cmath>
using namespace std;
const double PI  = acos(-1.0);
const double EPS = 1e-10;
struct date
{
    double x,y;
}lt,rt,ml,mr;
inline double max( double a,double b ){return a>b?a:b;}
double work( date temp )
{
    double a = mr.x - ml.x;
    double b =  pow(temp.x - ml.x,2) + pow(temp.y - ml.y,2);
    double c =  pow(temp.x - mr.x,2) + pow(temp.y - mr.y,2);
    double res = (b+c-a*a)/(2.*sqrt(b)*sqrt(c));
    return acos(res)*180/PI;
}
int main( )
{
    date ans1,ans2; double res1,res2;
    while( scanf("%lf%lf%lf",&ml.x,&mr.x,&mr.y) != EOF )
    {
        ml.y = mr.y;
        scanf("%lf%lf%lf%lf",&lt.x,&lt.y,&rt.x,&rt.y);
        double ang = 0;
        if( lt.y == mr.y && lt.x >= ml.x && lt.x <= mr.x )
        {
            printf("180.00000000\n");
            continue;
        }
        if( rt.y == mr.y && rt.x >= ml.x && rt.x <= mr.x )
        {
            printf("180.00000000\n");
            continue;
        }
        if( lt.y == rt.y && lt.y == mr.y )
        if( lt.x <= ml.x && rt.x >= mr.x )
        {
            printf("180.00000000\n");
            continue;
        }
        while( abs(rt.x - lt.x) > 0.00000000001 || abs(rt.y - lt.y) > 0.00000000001 )
        {
            ans1.x = ( lt.x+lt.x+rt.x )/3.;
            ans1.y = ( lt.y+lt.y+rt.y )/3;

            ans2.x = ( rt.x+rt.x+lt.x )/3.;
            ans2.y = ( rt.y+rt.y+lt.y )/3;

            res1 = work(ans1); res2 = work(ans2);
            if( res1 < res2 )
                 lt = ans1;
            else rt = ans2;
            ang = max( res1,res2 );
        }
        printf("%.8lf\n",ang);
    }
    return 0;
}