Convert Integer to Hex String Without sprintf or itoa functions

Code

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

void print_hex(uint16_t num) {
    char digits[17] = "0123456789ABCDEF";
    uint8_t res[10];
    uint8_t idx = 0;
    
    if (num == 0) {
        putchar('0');
        return;
    }

    while (num > 0) {
        res[idx++] = digits[num % 16];
        num /= 16;
    }

    for (int i = idx - 1; i >= 0; i--) {
        putchar(res[i]);
    }
}

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

Solving Approach