Reverse a String In-Place

#include <stdio.h>

void swap(char* a, char* b){
    char tmp = *a;
    *a = *b;
    *b = tmp;
}

int strlen(const char* s){
    int len = 0;
    while(*s != '\0'){
        len++;
        s = s + 1;
    }
    return len;
}

void reverse_string(char *str) {
    // Your logic here
    int len = strlen(str);
    char* rear = str + len - 1;
    for(int i = 0; i < len / 2; i++){
        swap(str, rear);
        str = str + 1;
        rear = rear - 1;
    }
}

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;
}