Reverse of a number with leading zeroes

Question

How do we reverse a number with leading zeroes in number ? For ex: If input is 004, output should be 400.

I wrote below program but it works only when n

Answer 1

A recursive approach, but easily converted to a loop...

#include 

int f(int value = 1)
{
    char c;
    return (std::cin.get(c) && isdigit(c))
           ? (c - '0') * value + f(10 * value)
           : 0;
}


int main()
{
    std::cout << f() << '\n';
}