Find the reverse of a number (ex : 2500 reverse 0025) without the help of string or character

Question

Is there any technique for finding the reverse when there are zeros at the end.

While following the algorithm of %10 technique the result is 52. And the 0\'s are mis

Answer 1

I think the accepted answer is a good one, in that it both refutes the parts of the question that are wrong and also offers a solution that will work. However, the code there is all Java, and it doesn't expose the prettiest API. Here's a C++ version that based on the code from the accepted answer.

(Ha ha for all my talk, my answer didn't reverse the string! Best day ever!)

After going back to school and getting a degree, I came up with this answer: it has the makes the somewhat dubious claim of "not using strings" or converting any values to string. Can't avoid characters, of course, since we are printing the value in the end.

#include 
#include 

class ReverseLong {
  public:

    ReverseLong(long value) {
      long num = value;
      bool leading = true;
      this->value = 0;
      this->leading_zeros = 0;

      while (num != 0) {
        int digit = num % 10;
        num = num / 10;

        if (leading && digit == 0) {
          this->leading_zeros += 1;
        } else {
          this->value = this->value * 10 + digit;
          leading = false;
        }
      }
    };

    friend std::ostream & operator<<(std::ostream& out, ReverseLong const & r);

  private:
    long value;
    int leading_zeros;

};

std::ostream & operator<<(std::ostream& out, ReverseLong const & r) {

  for (int i =0; i < r.leading_zeros; i++) {
    out << 0;
  }

  out << r.value;

  return out;
};

int main () {
  ReverseLong f = ReverseLong(2500); // also works with numbers like "0"!

  std::cout << f << std::endl; / prints 0052
};