Fraction to Recurring Decimal in C++

Suppose we have two integers representing the numerator and denominator of a fraction, we have to find fraction in string format. If the fractional part is repeating, enclose the repeating part in parentheses. So if the numerator is 2 and denominator is 3, then the output will be “0.(6)”

To solve this, we will follow these steps −

• if numerator is 0, then return 0

• define one array ans

• if the numerator < 0 and denominator > 0 or numerator 0 and denominator < 0, then insert negative symbol ‘-’ into the ans array

• divisor := |numerator| and dividend := |denominator|, remainder := divisor mod dividend

• x := string of divisor / dividend

• insert each character from x into ans array

• if remainder = 0, then return ans array as a string.

• insert dot ‘.’ into ans

• define one map m

• while remainder is not 0

  • if remainder is present in m, then

    • insert opening parentheses at index m[remainder] of ans

    • insert closing parentheses into the ans at the end

    • break the loop

  • otherwise

    • m[remainder] := size of ans

    • remainder := remainder * 10

    • insert (remainder / dividend) as character into ans

    • remainder := remainder mod dividend

• return ans array as string.

Let us see the following implementation to get better understanding −

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
   public:
   string fractionToDecimal(int numerator, int denominator) {
      if(numerator == 0)return "0";
      vector <char> ans;
      if(numerator < 0 && denominator > 0 || numerator > 0 && denominator < 0)ans.push_back('-');
      long divisor = labs(numerator);
      long dividend = labs(denominator);
      long remainder = divisor % dividend;
      string x = to_string(divisor/dividend);
      for(int i = 0; i < x.size(); i++){
         ans.push_back(x[i]);
      }
      if(remainder == 0){
         return string(ans.begin(), ans.end());
      }
      ans.push_back('.');
      map <int, int> m;
      while(remainder != 0){
         if(m.find(remainder)!=m.end()){
            ans.insert(ans.begin() + m[remainder], '(');
            ans.push_back(')');
            break;
         }else{
            m[remainder] = ans.size();
            remainder *= 10;
            ans.push_back((remainder / dividend) + '0');
            remainder %= dividend;
         }
      }
      return string(ans.begin(), ans.end());
   }
};
main(){
   Solution ob;
   cout << ((ob.fractionToDecimal(100,6)));
}

Input

100
6

Output

16.(6)