poj1905 Expanding Rods 二分

标签：poj   c++   

Description

When a thin rod of length L is heated n degrees, it expands to a new length L‘=(1+n*C)*L, where C is the coefficient of heat expansion. 
When a thin rod is mounted on two solid walls and then heated, it expands and takes the shape of a circular segment, the original rod being the chord of the segment. 

Your task is to compute the distance by which the center of the rod is displaced. 

Input

Output

Sample Input

1000 100 0.0001
15000 10 0.00006
10 0 0.001
-1 -1 -1

Sample Output

61.329
225.020
0.000

#include<iostream>
#include<cstring>
#include<cmath>
#include<cstdio>
using namespace std;

int main(){
    double l,n,c;
    while(cin>>l>>n>>c){
        if(l<0&&n<0&&c<0)   break;
        double down=0.0;
        double up=l/2;
        double s=(1+n*c)*l;
        double h,mid,r;

        while(up-down>1e-5){
            mid=(up+down)/2;
            r=(l*l+4*mid*mid)/(8*mid);
            if(2*r*asin(l/(r*2))>s)
                up=mid;
            else  down=mid;
        }
        h=mid;
        printf("%.3lf\n",h);
    }
    return 0;
}

poj1905 Expanding Rods 二分

标签：poj   c++   

原文地址：http://blog.csdn.net/hyccfy/article/details/41380747