How to Copy a Stack in C++?

In C++, stacks are a type of container adaptor with a LIFO(Last In First Out) type of working, where a new element is added at one end (top) and an element is removed from that end only. In this article, we are going to discuss how to copy a stack in C++.

Copying a Stack to Another in C++

To copy a std::stack, we can simply use the copy constructor or copy assignment operator of std::stack that takes another stack as a parameter and creates a new stack with the same elements.

Syntax

stack<type> myStack2(myStack1);     // copy constructor
myStack2  = myStack1      // copy assignment operator

C++ Program to Copy a Stack

C++

// C++ program to illustrate how to copy a stack
#include <iostream>
#include <stack>
using namespace std;

int main()
{
    // Declaring a stack of integers
    stack<int> originalStack;

    // Pushing integers into the original stack
    originalStack.push(1);
    originalStack.push(2);
    originalStack.push(3);

    // Copying the original stack to a new stack
    stack<int> newStack = originalStack;

    // Checking if the new stack is empty
    if (newStack.empty()) {
        cout << "New stack is empty." << endl;
    }
    else {
        cout << "New stack is not empty." << endl;
    }

    return 0;
}

Output

New stack is not empty.

Time complexity: O(N), where n is the number of elements in the stack.
Auxiliary space: O(N)