Learn about how to use STL Stack in C++. The syntax to start using stack in C++ is std::stack.
In this tutorial, I will discuss the uses, applications, and examples for stacks in C++. After this, you will be able to solve most of the stack-related algorithm questions without implementing your own stack data structure. That is by using the inbuild STL std::stack in C++.
What is Stack?
Stacks are a sort of container adapter that works on the LIFO (Last In First Out) principle, in which a new element is added to one end (top) and an element is deleted from the opposite end (bottom).
The underlying container of a stack is an encapsulated object of either vector or deque (by default) or list (sequential container class), with a specific set of member functions to access its elements.
Syntax
To use the STL you have to include the stack file. But if you are using standard c++ 11 then it comes included in most of the standard library of C++.
#include<stack>Features of std::stack in c++
STL Stack provides the following methods that are available in the stack library or stack implementation to use.
- push(s): Push the element s on top of the stack.
- pop(): This function returns the top-most element and then deletes the element from the stack.
- top(): Returns the top of the stack element.
- size(): Returns the total number of elements present at that time in stack.
- empty(): Return true if stack is empty, Otherwise if stack is not empty false is returned.
Implementation
Let me show is a small implementation of STL std::stack in practice. Similarly, you can use the stack in your applications or coding interview questions.
#include <iostream>
#include <stack>
using namespace std;
// Stack implementation with use of `std::stack` in C++.
int main()
{
stack<string> newStack;
newStack.push("First Push"); // Insert `A` into the stack
newStack.push("Second Push"); // Insert `B` into the stack
newStack.push("Third Push"); // Insert `C` into the stack
newStack.push("Fourth Push"); // Insert `D` into the stack
// prints the top of the stack (`Fourth Push`)
cout << "The top element is " << newStack.top() << endl;
// returns the total number of elements present in the stack newStack
cout << "The stack size is " << newStack.size() << endl;
newStack.pop(); // removing the top element (`Fourth Push`)
newStack.pop(); // removing the next top (`Third Push`)
//Removing all the elements from the stack.
cout << "The stack size is " << newStack.size() << endl;
// check if the stack is empty
if (newStack.empty()) {
cout << "The stack is empty\n";
}
else {
cout << "The stack is not empty\n";
}
//The Stack is Empty is printed as all the elements present in the stack are poped out.
return 0;
}
Output:
The top element is Fourth Push
The stack size is 4
The stack size is 2
The stack is not empty
Wrap Up
If you liked our post related to the stack implementation in c++ then please follow us on Facebook and Twitter. Let us know the questions and answer you want to cover in this blog.
Further Read:
