K&R exercise 3.5 - C (СИ)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
int main()
{
    int i, c;
    char s[30];
    for (i=0; (s[i] = getchar()) != EOF; i++ )
    ;
    s[i] = '\0';
    reverse(s);
    for (i=0; s[i] != '\0'; i++)
        printf("%c", s[i]);
    itos(12345, s, 16);
    printf('\n');
    for (i=0; s[i] != '\0'; i++)
        printf("%c", s[i]);
    return 0;
}
 
void itos (int n, char s[], int b)
{
    int i = 0,k, sign;
    if (n < 0)
    {
        sign = '-';
        n = -n;
    }
 
    do
    {
        n /= b;
        k = n % b;
        s[i++] = (k > 9) ? (k +'a' - 10) : k;
    } while (n > 0);
    s[i] = '\0';
    reverse(s);
}
 
void reverse (char s[])
{
    int i, j, c;
    for (i = 0, j = strlen(s) - 1; i < j; i++, j--)
    {
        c = s[i];
        s[i] = s[j];
        s[j] = c;
    }
}