/*

Reverse a string using 2 pointer Approach

Problem Statement: Reverse the given string from user.

For e.g initial string: hello, reversed string: olleh.

Using two pointer approach, firstly 'h' and 'o' are swapped similarly other characters follow the same sequence.

In this way, the string is reversed without using extra space.

*/

import java.util.*;

import java.lang.*;

import java.io.*;

class reverse_string{

// function for reversing the given string

public static void ReverseTheString(){

Scanner sc = new Scanner(System.in);

String input = sc.nextLine();

int k = input.length();

//converting it into array to access each Character of string

char[] output = input.toCharArray();

//using two pointer type approach to swap the characters of string

//one pointer points to starting and other to ending

for(int itr = 0, ptr = k-1; itr < ptr; itr++, ptr--){

char flag = output[itr];

output[itr] = output[ptr];

output[ptr] = flag;

}

System.out.print("Reversed string: ");

for(int itr = 0; itr < k; itr++){

System.out.print(output[itr]);

}

}

public static void main (String[] args) throws java.lang.Exception{

//calling for the reverse function from main

ReverseTheString();

}

}

/*

Test Cases:

1.

Input -

towerofhanoi

Output -

Reversed string: ionahforewot

2.

Input -

reversemalayalam

Output -

Reversed string: malayalamesrever

Time Complexity: O(k), for traversing the array of characters where 'k' is the size of input string

Space Complexity: O(1), no extra space is used

*/