UVa 11666 - Logarithms

Accepted date: 2015-09-14
Ranking (as of 2015-09-14): 3 out of 433
Language: C++

/*
  UVa 11666 - Logarithms

  To build using Visual Studio 2012:
    cl -EHsc -O2 UVa_11666_Logarithms.cpp
*/

#include <cstdio>
#include <cmath>
#include <climits>

/*
  n / exp(L) = 1 - abs(x) < 1
  if x >= 0
    n / exp(L) = 1 - x < 1
  else if x < 0
    n / exp(L) = 1 - x > 1
  else
    n / exp(L) = 1
*/

int main()
{
  const int L_max = 21 /* static_cast<int>(log(static_cast<double>(INT_MAX))) */;
  double exp_Ls[L_max + 1];
  for (int i = 0; i <= L_max; i++)
    exp_Ls[i] = exp(static_cast<double>(i));
  while (true) {
    int n;
    scanf("%d", &n);
    if (!n)
      break;
    for (int L = 0; L <= L_max; L++) {
      double x = 1.0 - n / exp_Ls[L];
      if (fabs(x) < 1.0 &&
        (n < exp_Ls[L] && x > 0.0 || n > exp_Ls[L] && x < 0.0 ||
        n == exp_Ls[L] && x == 0.0)) {
        printf("%d %.8lf\n", L, x);
        break;
      }
    }
  }
  return 0;
}