Reverse a String In-Place

#include <stdio.h>

void reverse_string(char *str) {
    // find length of string
    int str_len = 0;
    while (str[str_len] != '\0') {
        str_len++;
    }
    str_len -= 1; //exclude \0
    
    int swap_range = (str_len / 2) + (str_len % 2); // for swapping we need half of string's length
    char buffer = ' ';
    
    for (int i = 0; i < swap_range; i++) {
        buffer = str[str_len - i];
        str[str_len - i] = str[i];
        str[i] = buffer;
    }
}

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

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

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