Capicua (v. 1.0.1)

// apple xcode
// paulogp

/* capicua: numeros e strings */
#include <stdio.h>
#include <string.h>

int capicua (char *the_input);

int capicua (char *the_input)
{
    unsigned long i, j;

    if (the_input != NULL) // when using fgets with strtok else strlen(the_input)
    {
        for (i = 0, j = strlen(the_input) - 1; i < j; i++, j--)
        {
            if (the_input[i] != the_input[j])
                return 0;
        }
    }
    else
    {
        return -1; // invalid input (\n)
    }

    return 1;
}

int main (int argc, const char * argv[])
{
    char the_input[20]; // max 20 digits
    char *the_input_ptr;
    int the_result;

    printf("inserir: ");
    fgets(the_input, sizeof(the_input), stdin);
    // removes \n from the end
    // NOTE: the_file_ptr points to the_file_name
    the_input_ptr = strtok (the_input, "\n");

    the_result = capicua (the_input_ptr);
    switch (the_result) {
        case 0:
            puts ("nao e capicua");
            break;

        case 1:
            puts ("capicua");
            break;

        default:
            puts ("invalido");
            break;
    }

    return 0;
}