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[UVA][二分] 10566 - Crossed Ladders

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Problem H
Crossed Ladders
Input: Standard Input

Output: Standard Output

Time Limit: 1 Second

 

A narrow street is lined with tall buildings. An x foot long ladder is rested at the base of the building on the right side of the street and leans on the building on the left side. A y foot long ladder is rested at the base of the building on the left side of the street and leans on the building on the right side. The point where the two ladders cross is exactly c feet from the ground. How wide is the street?

Each line of input contains three positive floating point numbers giving the values of x, y, and c.

For each line of input, output one line with a floating point number giving the width of the street in feet, with three decimal digits in the fraction.

Sample Input                             Output for Sample Input

30 40 10
12.619429 8.163332 3
10 10 3
10 10 1
 
 
26.033
7.000
8.000
9.798

做法 : 二分答案
利用相似形的觀念可以得到當距離 d 被決定的時候, c 的解

#include <stdio.h>
#include <math.h>
#define eps 1e-5

int main() {
    double c, x, y;
    while(scanf("%lf %lf %lf", &x, &y, &c) == 3) {
        double l = 0, r = x < y ? x : y, d, tc;
        while(1) {
            d = (l+r)/2;
            tc = sqrt(y*y-d*d)*sqrt(x*x-d*d)/(sqrt(y*y-d*d)+sqrt(x*x-d*d));
            if(fabs(tc-c) <= eps)
                break;
            if(tc > c)
                l = d;
            else
                r = d;
        }
        printf("%.3lf\n", d);
    }
    return 0;
}

我要檢舉
#10566#Crossed Ladders
台長： Morris

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