Convert Decimal Number to Binary or Hex Without itoa function

Code

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


char to_hex(uint8_t n) {
    char result;
    if (n <= 9) {
        result = '0' + n;
    }
    else {
        result = 'A' + n - 10;
    }

    return result;
}


void print_base(uint16_t num, uint8_t base) {
    char tmp_hex[5];
    int i;

    switch (base) {
    case 16:
        for (i = 3; i >= 0; --i) {
            tmp_hex[i] = to_hex((num >> (4*i)) & 0x0f);
        }
        for (i = 3; tmp_hex[i] == '0' && i >= 1; --i);
        for (;i >= 0; --i) {
            printf("%c", tmp_hex[i]);
        }
        break; 
    case 2:
        for (i = 15; (((num >> i) & 1) == 0) && i >= 1; --i);
        for (;i >= 0; --i) {
            printf("%c", ((num >> i) & 1) + '0');
        }
        break;
    }
}

int main() {
    uint16_t num;
    uint8_t base;
    scanf("%hu %hhu", &num, &base);

    print_base(num, base);
    return 0;
}

Solving Approach