converting a float to a fraction.

[dmmckelv]

Can anyone help me get started on converting a float to a fraction?

[~s.o.s~]

Be more specific, state your context and post your latest code attempt. Being vague wont help you at all.

[mathematician]

Can anyone help me get started on converting a float to a fraction?

In theory all you've got to do is use the decimal as the numerator, and then count up the number of digits in that numerator before putting a 1, followed by the same number of zeros on the bottom. So 0.25 becomes 25/100, for example. If you wanted to reduce it further than that, you would have to go round a loop looking for the largest common factor; starting, in this case with 25. Also in this case, you would only have to go round it once.

[zouyu1983]

#include <iostream>
using namespace std;
struct Fraction
{
 int numerator,
  denominator;
};
int FindCommonFactor(int m, int n)
{
 int x;
 while (m % n)
 {
  x = m % n;
  m = n;
  n = x;
 }
 return n;
}
void Process(char str[], Fraction fraction[], int &result)
{
 int strLen = strlen(str);
    const int displace = strLen - 4;
 const int usefulLen = displace - 1;
 int constDenominator,
  constNumerator = 0,
  cycleDenominator,
  cycleNumerator = 0,
  cycleDenominatorAdd = 0,
  cycleDenominatorMain,
  i,
  k = 1;
    for (i=1; i<usefulLen; i++)
 {
  constNumerator += int(str[displace - i] - 48) * k;
  k *= 10;
 }
 cycleDenominatorMain = constDenominator = k;
// cout << cycleDenominatorMain << endl << constNumerator << endl << usefulLen << endl;
 k = 1;
 int arrayDisplace = 0;
 for (i=0; i<usefulLen; i++)
 {
        cycleNumerator += ( int(str[displace - i] - 48) * k );
 
  cycleDenominatorAdd += ( 9 * k );
 //     cout << cycleNumerator << endl << cycleDenominatorAdd << endl << cycleDenominatorMain << endl;
        cycleDenominator = cycleDenominatorAdd * cycleDenominatorMain;
//      cout << cycleNumerator << endl << cycleDenominator << endl;
        fraction[arrayDisplace].numerator = cycleDenominatorAdd * constNumerator + cycleNumerator;
  fraction[arrayDisplace].denominator = cycleDenominator;
 //       cout << fraction[arrayDisplace].numerator << endl << fraction[arrayDisplace].denominator << endl;
  int maxFactor = FindCommonFactor(fraction[arrayDisplace].denominator, fraction[arrayDisplace].numerator);
 
  fraction[arrayDisplace].denominator /= maxFactor;
  fraction[arrayDisplace].numerator /= maxFactor;
  arrayDisplace++;
        k *= 10;
  constNumerator /= 10;
  constDenominator /= 10;
  cycleDenominatorMain = constDenominator;
 }
 int sum = fraction[0].denominator;
     result = 0;
 for (i=0; i<arrayDisplace; i++)
 {
  if (sum > fraction[i].denominator)
  {
   sum = fraction[i].denominator;
   result = i;
  }
 }
// cout << i << endl << fraction[i].numerator << "/" << fraction[i].denominator << endl;
 return;
}
int main()
{
 char str[14];
 Fraction fraction[9];
 while (cin >> str)
 {
  if (strlen(str) == 1 && str[0] == '0')
  {
   break;
  }
  int result;
  Process(str, fraction, result);
  cout << fraction[result].numerator << "/" << fraction[result].denominator << endl;
 }
 return 0;
}

i wrote this code when i was a freshman,
it coded for one problem in online judge of fuzhou university
i hope it will help to you