Написать функцию itoa (n,s) преобразования целого числа n в стринг s

void itoa(long val, char* buf)
{
    unsigned radix = 10;
    char *p;                 /* pointer to traverse string */
    char *firstdig;          /* pointer to first digit */
    char temp;               /* temp char */
    unsigned digval;         /* value of digit */
 
    p = buf;
 
    if (val < 0) {
        /* negative, so output '-' and negate */
        *p++ = '-';
        val = (unsigned long)(-val);
    }
 
    firstdig = p;           /* save pointer to first digit */
 
    do {
        digval = (unsigned) (val % radix);
        val /= radix;       /* get next digit */
 
        /* convert to ascii and store */
        if (digval > 9)
            *p++ = (char) (digval - 10 + 'a');  /* a letter */
        else
            *p++ = (char) (digval + '0');       /* a digit */
 
    } while (val > 0);
 
    /* We now have the digit of the number in the buffer, but in reverse
    order.  Thus we reverse them now. */
 
    *p-- = '\0';            /* terminate string; p points to last digit */
 
    do {
        temp = *p;
        *p = *firstdig;
        *firstdig = temp;   /* swap *p and *firstdig */
        --p;
        ++firstdig;         /* advance to next two digits */
    } while (firstdig < p); /* repeat until halfway */
}