Convert Hexadecimal String to Integer Without strtol or sscanf functions

Code

#include <stdio.h>
#include <stdint.h>
void up_case(char *str) {
    for (int i = 0; str[i]; i++) {
        if (str[i] >= 'a' && str[i] <= 'z')
            str[i] = str[i] - ('a' - 'A');
    }
}
uint16_t hex_to_uint(const char *str) {
    // Your logic here
    int val = 0;
    for (int i = 0; str[i]; i++) {
        char c = str[i];
        int digit = (c >= 'A') ? (c - 'A' + 10) : (c - '0');
        val = (val << 4) | digit;
    }
    return val;
}

int main() {
    char hex[10];
    scanf("%s", hex);
    up_case(hex);
    printf("%u", hex_to_uint(hex));
    return 0;
}

Solving Approach