Desafio Palíndromo Pamdigital

// http://www.forum-invaders.com.br/vb/showthread.php/42844-DESAFIO-Pal%C3%ADndromo-Pamdigital

#include <stdio.h>
#include <math.h>
#include <time.h>
#include <windows.h>

typedef unsigned char bin_t[20];
typedef unsigned int dec_t;

dec_t reverseDigits(dec_t num)
{
    dec_t rev_num = 0;
    while(num > 0)
    {
        rev_num = rev_num * 10 + (num % 10);
        num = num * 0.1;
    }
    return rev_num;
}

dec_t nextPalindrome(dec_t n) {
    n++;

    int digits = 0;
    dec_t num = n;
    do {
        digits++;
    } while((num *= 0.1) > 0);

    if(digits == 1)
        return n;

    dec_t half = digits * 0.5;
    dec_t left = n * pow(0.1, half);
    dec_t r_left = reverseDigits(left);
    if(r_left % 2 == 0) {
        return nextPalindrome(((int)(n * pow(0.1, digits-1)) + 1) * pow(10, digits-1));
        r_left = reverseDigits(left);
    }
    dec_t p10h  = pow(10, half);
    dec_t right = n - (left * p10h);

    if(digits % 2) {
        r_left = reverseDigits(left * 0.1);

        if(r_left > right)
            return (left * p10h) + r_left;
        else {
            ++left;
            return (left * p10h) + reverseDigits(left * 0.1);
        }
    } else {
        if(r_left > right)
            return (left * p10h) + r_left;
        else {
            ++left;
            return (left * p10h) + reverseDigits(left);
        }
    }
}

int isPalindromeBin(dec_t dec) {
    bin_t bin = {0};
    int digits = -1;
    int i = 0;

    do {
        bin[++digits] = dec % 2;
    } while((dec >>= 1) > 0);

    int half = digits / 2;

    for(i = 0; i <= half; ++i)
        if(bin[i] != bin[digits - i])
            return 0;

    return 1;
}

int main()
{
    dec_t r = 0;
    dec_t v = 1;

    while(v <= 1000000) {
        if(isPalindromeBin(v))
            r += v;
        v = nextPalindrome(v);
    }

    printf("%d", r);
    return 0;
}