Reversing a Stack with the help of another empty Stack
Last Updated :
23 Jul, 2025
Given a Stack consisting of N elements, the task is to reverse the Stack using an extra stack.
Examples:
Input: stack = {1, 2, 3, 4, 5}
Output:
1
2
3
4
5
Explanation:
Input Stack:
5
4
3
2
1
Reversed Stack:
1
2
3
4
5
Input: stack = {1, 3, 5, 4, 2}
Output:
1
3
5
4
2
Approach 1: Follow the steps below to solve the problem:
Below is the implementation of the above approach.
C++
// C++ program to reverse a stack
// by using an extra stack
#include <bits/stdc++.h>
using namespace std;
// Function to transfer elements of
// the stack s1 to the stack s2
void transfer(stack<int>& s1,
stack<int>& s2, int n)
{
for (int i = 0; i < n; i++) {
// Store the top element
// in a temporary variable
int temp = s1.top();
// Pop out of the stack
s1.pop();
// Push it into s2
s2.push(temp);
}
}
// Function to reverse a stack using another stack
void reverse_stack_by_using_extra_stack(stack<int>& s,
int n)
{
stack<int> s2;
for (int i = 0; i < n; i++) {
// Store the top element
// of the given stack
int x = s.top();
// Pop that element
// out of the stack
s.pop();
transfer(s, s2, n - i - 1);
s.push(x);
transfer(s2, s, n - i - 1);
}
}
// Driver Code
int main()
{
int n = 5;
stack<int> s;
s.push(1);
s.push(2);
s.push(3);
s.push(4);
s.push(5);
reverse_stack_by_using_extra_stack(s, n);
for (int i = 0; i < n; i++) {
cout << s.top() << " ";
s.pop();
}
return 0;
}
// Java program to reverse a stack
// by using an extra stack
import java.io.*;
import java.util.*;
class GFG{
// Function to transfer elements of
// the stack s1 to the stack s2
static void transfer(Stack<Integer> s1,
Stack<Integer> s2, int n)
{
for(int i = 0; i < n; i++)
{
// Store the top element
// in a temporary variable
int temp = s1.peek();
// Pop out of the stack
s1.pop();
// Push it into s2
s2.push(temp);
}
}
// Function to reverse a stack using another stack
static void reverse_stack_by_using_extra_stack(Stack<Integer> s,
int n)
{
Stack<Integer> s2 = new Stack<Integer>();
for(int i = 0; i < n; i++)
{
// Store the top element
// of the given stack
int x = s.peek();
// Pop that element
// out of the stack
s.pop();
transfer(s, s2, n - i - 1);
s.push(x);
transfer(s2, s, n - i - 1);
}
}
// Driver Code
public static void main(String[] args)
{
int n = 5;
Stack<Integer> s = new Stack<Integer>();
s.push(1);
s.push(2);
s.push(3);
s.push(4);
s.push(5);
reverse_stack_by_using_extra_stack(s, n);
for(int i = 0; i < n; i++)
{
System.out.print(s.peek() + " ");
s.pop();
}
}
}
// This code is contributed by Dharanendra L V.
# Python3 program to reverse a stack
# by using an extra stack
# Function to transfer elements of
# the stack s1 to the stack s2
def transfer(s1, s2, n):
for i in range(n):
# Store the top element
# in a temporary variable
temp = s1[-1]
# Pop out of the stack
s1.pop()
# Push it into s2
s2.append(temp)
# Function to reverse a stack using another stack
def reverse_stack_by_using_extra_stack(s, n):
s2 = []
for i in range(n):
# Store the top element
# of the given stack
x = s[-1]
# Pop that element
# out of the stack
s.pop()
transfer(s, s2, n - i - 1)
s.append(x)
transfer(s2, s, n - i - 1)
# Driver Code
if __name__ == "__main__":
n = 5
s = []
s.append(1)
s.append(2)
s.append(3)
s.append(4)
s.append(5)
reverse_stack_by_using_extra_stack(s, n)
for i in range(n):
print(s[-1], end = " ")
s.pop()
# This code is contributed by ukasp
// C# program to reverse a stack
// by using an extra stack
using System;
using System.Collections.Generic;
class GFG{
// Function to transfer elements of
// the stack s1 to the stack s2
static void transfer(Stack<int> s1,
Stack<int> s2, int n)
{
for (int i = 0; i < n; i++) {
// Store the top element
// in a temporary variable
int temp = s1.Peek();
// Pop out of the stack
s1.Pop();
// Push it into s2
s2.Push(temp);
}
}
// Function to reverse a stack using another stack
static void reverse_stack_by_using_extra_stack(Stack<int> s,
int n)
{
Stack<int> s2 = new Stack<int>();
for (int i = 0; i < n; i++) {
// Store the top element
// of the given stack
int x = s.Peek();
// Pop that element
// out of the stack
s.Pop();
transfer(s, s2, n - i - 1);
s.Push(x);
transfer(s2, s, n - i - 1);
}
}
// Driver Code
public static void Main()
{
int n = 5;
Stack<int> s = new Stack<int>();
s.Push(1);
s.Push(2);
s.Push(3);
s.Push(4);
s.Push(5);
reverse_stack_by_using_extra_stack(s, n);
for (int i = 0; i < n; i++) {
Console.Write(s.Peek() + " ");
s.Pop();
}
}
}
// This code is contributed by SURENDRA_GANGWAR.
<script>
// JavaScript program to reverse a stack
// by using an extra stack
// Function to transfer elements of
// the stack s1 to the stack s2
function transfer(s1, s2, n)
{
for (i = 0; i < n; i++) {
// Store the top element
// in a temporary variable
var temp = s1[s1.length-1];
// Pop out of the stack
s1.pop();
// Push it into s2
s2.push(temp);
}
}
// Function to reverse a stack using another stack
function reverse_stack_by_using_extra_stack(s,n)
{
var s2 = [];
var i;
for (i = 0; i < n; i++) {
// Store the top element
// of the given stack
var x = s[s.length-1];
// Pop that element
// out of the stack
s.pop();
transfer(s, s2, n - i - 1);
s.push(x);
transfer(s2, s, n - i - 1);
}
}
// Driver Code
var n = 5;
var s = []
s.push(1);
s.push(2);
s.push(3);
s.push(4);
s.push(5);
reverse_stack_by_using_extra_stack(s, n);
var i;
for (i = 0; i < n; i++) {
document.write(s[s.length-1] + ' ');
s.pop();
}
</script>
Time Complexity: O(N2)
Auxiliary Space: O(N)
Approach 2: Follow the steps below to solve the problem:
- Initialize an empty stack called ans.
- Pop the top element of the given stack S and push it into the stack ans.
- Return the stack ans, which will contain the reversed elements of the stack S.
Below is the implementation of the above approach.
C++
#include<bits/stdc++.h>
using namespace std;
stack<int> reverse_stack_by_using_extra_stack(stack<int> s, int n){
stack<int> ans;
for(int i = 0; i < n; i++){
ans.push(s.top());
s.pop();
}
return ans;
}
// Nikunj Sonigara
int main()
{
int n = 5;
stack<int> s;
s.push(1);
s.push(2);
s.push(3);
s.push(4);
s.push(5);
s = reverse_stack_by_using_extra_stack(s, n);
for (int i = 0; i < n; i++) {
cout << s.top() << " ";
s.pop();
}
return 0;
}
import java.util.Stack;
class GFG {
static Stack<Integer> reverseStackByUsingExtraStack(Stack<Integer> s, int n) {
Stack<Integer> ans = new Stack<>();
for (int i = 0; i < n; i++) {
ans.push(s.pop());
}
return ans;
}
public static void main(String[] args) {
int n = 5;
Stack<Integer> s = new Stack<>();
s.push(1);
s.push(2);
s.push(3);
s.push(4);
s.push(5);
s = reverseStackByUsingExtraStack(s, n);
for (int i = 0; i < n; i++) {
System.out.print(s.peek() + " ");
s.pop();
}
}
}
# Define a function to reverse a stack using an extra stack
def reverse_stack_by_using_extra_stack(s, n):
ans = []
for i in range(n):
ans.append(s.pop())
return ans
# Main function
if __name__ == "__main__":
n = 5
# Create a stack and push elements into it
s = []
s.append(1)
s.append(2)
s.append(3)
s.append(4)
s.append(5)
# Reverse the stack using the function
s = reverse_stack_by_using_extra_stack(s, n)
# Print the reversed stack
for i in range(n):
print(s[-1], end=" ")
s.pop()
using System;
using System.Collections.Generic;
class Program
{
// Define a function to reverse a stack using an extra stack
static Stack<int> ReverseStackUsingExtraStack(Stack<int> s, int n)
{
Stack<int> reversedStack = new Stack<int>();
for (int i = 0; i < n; i++)
{
reversedStack.Push(s.Pop());
}
return reversedStack;
}
// Main function
static void Main()
{
int n = 5;
// Create a stack and push elements into it
Stack<int> s = new Stack<int>();
s.Push(1);
s.Push(2);
s.Push(3);
s.Push(4);
s.Push(5);
// Reverse the stack using the function
Stack<int> reversedStack = ReverseStackUsingExtraStack(s, n);
// Print the reversed stack
for (int i = 0; i < n; i++)
{
Console.Write(reversedStack.Peek() + " ");
reversedStack.Pop();
}
}
}
// This code is contributed by shivamgupta0987654321
<script>
// Define a function to reverse a stack using an extra stack
function reverseStackByUsingExtraStack(stack, n) {
let reversedStack = [];
for (let i = 0; i < n; i++) {
reversedStack.push(stack.pop());
}
return reversedStack;
}
// Main function
let n = 5;
// Create a stack and push elements into it
let stack = [];
stack.push(1);
stack.push(2);
stack.push(3);
stack.push(4);
stack.push(5);
// Reverse the stack using the function
stack = reverseStackByUsingExtraStack(stack, n);
// Print the reversed stack
for (let i = 0; i < n; i++) {
console.log(stack[stack.length - 1]);
stack.pop();
}
}
</script>
Time Complexity: O(N)
Auxiliary Space: O(N)
