Demo code inspired by Project Euler to determine if a number is palindromic.

palindromicNum.cpp

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <vector>

int main(int argc, char* argv[])
{
    if(argc == 1)
        return 0;

    const unsigned int NUMDIGITS = (atoi(argv[1]) == 0) ? 1 : (int)log10(abs(atoi(argv[1]))) + 1;
    const unsigned int NUM = atoi(argv[1]);
    unsigned int d = 0;
    double actual, fd, frac;
    double correction = 1e-9;
    std::vector<int> digits;

    printf("Number of digits [%d]\n", NUMDIGITS);
    actual = NUM / pow(10, NUMDIGITS - 1.0);
    frac = modf(actual + correction, &fd);
    printf("(1) Going in with num [%d] and actual [%f] and whole part [%f] and frac [%f]\n", NUM, actual, fd, frac);
    digits.push_back((int)fd);

    // Extract remaining digits.
    for(int i = 1; i < NUMDIGITS; i++)
    {
        actual = frac * 10.0;
        frac = modf(actual + correction, &fd);
        printf("(2) Going in with num [%d] and actual [%f] and whole part [%f] and frac [%f]\n", NUM, actual, fd, frac);
        digits.push_back((int)fd);
    }

    // Print individual digits.
    for(const auto& i : digits)
    {
        printf("%d ", i);
    }

    puts("\n");

    bool isPalindromicNumber = true;

    // Check if number is palindromic.
    for(int j = 0; j < digits.size() / 2; j++)
    {
        printf("%d ", digits[j]);

        if(digits[j] != digits[digits.size() - 1 - j])
        {
            isPalindromicNumber = false;
            break;
        }
    }

    puts("\n");

    if(isPalindromicNumber)
        puts("Number is palindromic\n");
    else
        puts("Number is not palindromic\n");

    return 0;
}