Convert Uppercase Letters to Lowercase

Code

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

void to_lowercase(char *str) {
    int i;
    int diff = 'a' - 'A';
    char c;
    
    i = 0;
    while(str[i])
    {
        c =str[i];
        if(c >= 'A' && c <= 'Z')
        {
            c = c + diff;
            str[i] = c;
        }
        i++;
    }
}

int main() {
    char str[101];
    fgets(str, sizeof(str), stdin);

    // Remove newline
    uint8_t i = 0;
    while (str[i]) {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    to_lowercase(str);
    printf("%s", str);
    return 0;
}

Solving Approach