Convert Hexadecimal String to Integer Without strtol or sscanf functions

Code

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


//(1A3F)₁₆ = (1 × 16³) + (10 × 16²) + (3 × 16¹) + (15 × 16⁰) = (6719)₁₀
uint16_t hex_to_uint(const char *str) {
    // Your logic here
uint16_t len = 0;
uint16_t result = 0;
while(str[len] != '\0')
{
    len++;
}
for(int i=0;i<len;i++)
{
    char c = str[i];
    uint16_t value = 0;

    if(c >= '0' && c <= '9')
    {
        value = c-'0';
    }else if(c >= 'A' && c <= 'F')
    {
        value = c - 'A'+10;
    }else if(c >= 'a' && c <= 'f')
    {
       value = c - 'a'+10; 
    }else{
        return 0;
    }
     result = result * 16 + value;


   
}
    return result;
}

int main() {
    char hex[10];
    scanf("%s", hex);

    printf("%u", hex_to_uint(hex));
    return 0;
}

Solving Approach