Implement various string algorithms in C++

Implement various string algorithms 

1. Reverse string

#include <iostream>
using namespace std;
int main(){
    char str[] = "Hello World";
    
    for(int i = 0; str[i] != '\0'; i++){
        for (int j = i+1; str[j] != '\0'; j++){
            char temp = str[i];
            str[i] = str[j];
            str[j] = temp;
        }
    }
    cout << str << endl;
}

2. Length of string

#include <iostream>
using namespace std;
int main(){
    char str[] = "Hello World";
    int len = 0;
    for(int i = 0; str[i] != '\0'; i++){
        len++;
    }
    cout << len << endl;
}

3.