UVa 10668 - Expanding Rods

Accepted date: 2016-06-16
Run Time: 0.000
Ranking (as of 2016-06-16): 190 out of 490
Language: C++

/*
  UVa 10668 - Expanding Rods

  To build using Visual Studio 2012:
    cl -EHsc -O2 UVa_10668_Expanding_Rods.cpp
*/

#include <limits>
#include <cstdio>
#include <cmath>
using namespace std;

int main()
{
  const double pi = 2.0 * acos(0.0), epsilon = numeric_limits<double>::epsilon();
  while (true) {
    double l, n, c;
    scanf("%lf %lf %lf", &l, &n, &c);
    if (l < 0.0 && n < 0.0 && c < 0.0)
      break;
    if (l < epsilon || n < epsilon || c < epsilon) {
      printf("%.3lf\n", 0.0);
      continue;
    }
    double nl = (1.0 + n * c) * l, mid;
    for (double low = 0.0, high = pi / 2.0; low - high < epsilon; ) {
      mid = (low + high) / 2.0;
#ifdef DEBUG
      printf("%.15lf %.15lf %.15lf\n", low, mid, high);
#endif
      double result = nl / mid - l / sin(mid);
      if (result > epsilon)
        low = mid;
      else if (result < -epsilon)
        high = mid;
      else
        break;
    }
    double r = nl / (mid * 2.0), d = r * (1.0 - cos(mid));
    printf("%.3lf\n", d);
  }
  return 0;
}