hdu 2438 Turn the corner

原题：http://acm.hdu.edu.cn/showproblem.php?pid=2438

这道题比较简单，得到公式再运用三分找凸点的方法很容易就能出来

代码：

#include <iostream>

#include <math.h>

using namespace std;

const double pi = acos(-1.0);// 三角反函数得到，pi的值，

bool TernarySearch(double x, double y, double l, double w){
double ans;
double left = 0, right = pi/2.0, ll, rr, len;//这里千万不能用 right = 90; 因为的这里的90是并不是90度的意思
len = (right - left)/3;
while (len > 0.00001){
ll = left + len;
rr = right - len;
double vll = l*cos(ll) + (w - x*cos(ll)) / sin(ll);
double vrr = l*cos(rr) + (w - x*cos(rr)) / sin(rr);
if (vll <= vrr)
left = ll;
else
right = rr;
len = (right - left) / 3;
}

ans = l*cos(ll) + (w - x*cos(ll)) / sin(ll);
if (ans <= y)
return true;
else
return false;

}

int main()

{
double x, y, l, w;
while (cin >> x >> y >> l >> w){
if (TernarySearch(x, y, l, w))
cout << "yes" << endl;
else
cout << "no" << endl;

}
return 0;

}