Reverse a String In-Place

#include <stdio.h>

int strlen(char *str){
    int length = 0;
    while (*str != '\0'){
        length++;
        str++;
    }

    return length;
}


void reverse_string(char *str) {
    char length = strlen(str);
    char *left = str;
    char *right = str + (length-1);
    while (left < right){
        char temp = *left;
        *left = *right;
        *right = temp;
        left++;
        right--;
    }
}

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;
}