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

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

char hexc[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

void print_hex(uint16_t num) {
    int i = 4;
    uint16_t mask = ((1 << 4) - 1) << 12;

    while (!(num & mask) && i) {
        i--;
        mask >>= 4;
    }

    if (!mask) {
        printf("0");
        return;
    }

    while (i--)
        printf("%c", hexc[(num >> (4 * i)) & 0xf]);
}

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