Oops!

#define MAX_NUM_OF_DIGITS   10
#define MAX_VALUE_OF_INT    0x7fffffff
#define MIN_VALUE_OF_INT    -0x80000000

int reverse(int x)
{
    int digits[MAX_NUM_OF_DIGITS] = { 0 };
    int sign = x > 0 ? 1 : 0;
    unsigned abs = sign ? x : -x;
    unsigned max = sign ? MAX_VALUE_OF_INT : -MIN_VALUE_OF_INT;
    unsigned result = 0;
    int i = 0;
    int num_digits = 0;

    while (abs) {
        digits[i++] = abs % 10;
        abs /= 10;
    }
    num_digits = i;

    for (i = 0; i < num_digits && i < 9; i++)
        result = 10 * result + digits[i];

    if (num_digits == MAX_NUM_OF_DIGITS) {
        /* overflow for 32-bit signed int */
        if (result > max / 10 ||
            (result == max / 10 && digits[9] > max % 10))
            return 0;
        else
            result = 10 * result + digits[i];
    }

    return sign ? result : -result;
}