reverse_a_string_using_stack.cpp

/* 
Given a string,print reverse of the string using stack
Approach:-
In stack,we know LIFO principle works.
First,i create an empty stack,then i push each character of string in stack
then,using for loop i popped out every single character.
*/

#include<iostream>
#include<string>
#include<stack>
using namespace std;

//function to reverse the string
void reverse(string &s)
{
	int i;
	//Creating empty stack
	stack<int> str;
	//pushing each character of the string into the stack
	for(char ch:s)
	{
        str.push(ch);
    	}
	//popping each character one by one from the stack
    	for(i=0;i<s.size();i++)
    	{
        s[i]=str.top();
        str.pop();
    	} 
}

//driver code
int main()
{
	cout<<"Program to reverse a string."<<endl;
	string s;
	cout<<"Enter a string you want to reverse:";
	cin>>s;
	//calling function
	reverse(s);
	//printing result
	cout<<s;
	return 0;
}

/*
Test Case :
1.
Input : Rahul
Output : luhaR
2.
Input : Sajal
Output : lajaS
Time Complexity : O(n), where n is the length of the input string.
Space Complexity : O(n) for stack.
*/