UVa 10566 Crossed Ladders

设宽度为w，二分w。

#include <cstdio>
#include <cmath>
#include <algorithm>

#define eps 1e-6

using namespace std;

int main()
{
    double x, y, c;
    while ( ~scanf( "%lf%lf%lf", &x, &y, &c ) )
    {
        double high = min( x, y );
        double low = 0.0;
        double mid;
        while ( low < high )
        {
            mid = ( low + high ) / 2.0;
            double cc = sqrt( x*x - mid*mid )*sqrt( y*y - mid*mid ) / ( sqrt( y*y - mid*mid ) + sqrt( x*x - mid*mid ) );
            if ( fabs( cc - c ) < eps )
            {
                break;
            }
            else if ( cc < c ) high = mid;
            else low = mid;
        }

        printf( "%.3f\n", mid );
    }
    return 0;
}