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  1. #include <iostream>
  2. #include <sstream>
  3. #include <utility>
  4. #include <string>
  5. #include <cmath>
  6. #include <limits>
  7.  
  8. typedef std::pair<int, int> Fraction;
  9.  
  10. int gcd(int a, int b) {
  11.     int c;
  12.     while (a != 0) {
  13.         c = a;
  14.         a = b % a;
  15.         b = c;
  16.     }
  17.     return b;
  18. }
  19.  
  20. int wholeDigits(double x) {
  21. 	if (x < 1)
  22. 		return 0;
  23.     return (int)log10(x) + 1;
  24. }
  25.  
  26. Fraction decToFrac(double x) {
  27.     bool isNegative = x < 0.0;
  28.     x = std::abs(x);
  29.  
  30.     if (x > std::numeric_limits<int>::max())
  31.         return std::make_pair(isNegative ? -1 : 1, 0);
  32.  
  33.     std::ostringstream os;
  34.     os.precision(9 - wholeDigits(x)); // int na wiecej nie pozwala
  35.     os << std::fixed << x;
  36.     std::string numStr = os.str();
  37.     int pointPos = numStr.find_last_of('.');
  38.     numStr.erase(pointPos, 1);
  39.     int fracDigits = numStr.size() - pointPos;
  40.  
  41.     int numerator;
  42.     std::istringstream is(numStr);
  43.     is >> numerator;
  44.  
  45.     int denominator = 1;
  46.     while (fracDigits--)
  47.         denominator *= 10;
  48.  
  49.     int d = gcd(numerator, denominator);
  50.     numerator /= d;
  51.     denominator /= d;
  52.  
  53.     if (isNegative)
  54.         numerator = -numerator;
  55.  
  56.     return std::make_pair(numerator, denominator);
  57. }
  58.  
  59. std::string print(Fraction f) {
  60.     std::ostringstream os;
  61.     os << f.first << " / " << f.second;
  62.     return os.str();
  63. }
  64.  
  65. int main() {
  66.     std::cout 
  67.         << print(decToFrac(1)) << std::endl
  68.         << print(decToFrac(100.1)) << std::endl
  69.         << print(decToFrac(0.001)) << std::endl
  70.         << print(decToFrac(123.456)) << std::endl
  71.         << print(decToFrac(-654.321)) << std::endl
  72.         << print(decToFrac(1e-15)) << std::endl
  73.         << print(decToFrac(1e15)) << std::endl;
  74. }
  75.  
Success #stdin #stdout 0s 3436KB
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stdin
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Standard input is empty
stdout
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1 / 1
1001 / 10
1 / 1000
15432 / 125
-654321 / 1000
0 / 1
1 / 0
https://ideone.com/KaURCf
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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