120. Convert Integer to Hex String Without sprintf or itoa functions

#include <stdio.h>
#include <stdint.h>

void print_hex(uint16_t num) 
{
    if(!num)
    {
        printf("0");
        return ;
    } 
    char a[17]={'\0'};
    char *ptr=&a[17];

    while(num)
    {
        ptr--;
       *ptr="0123456789ABCDEF"[num%16];
       //printf("%c",*ptr);
        num=num/16;
    }
    printf("%s\n",ptr);
}

int main() {
    uint16_t num;
    scanf("%hu", &num);
    print_hex(num);
    return 0;
}