The **Standard Template Library (STL)** in C++ contains the implementation of commonly known data structures such as [arrays](https://www.educative.io/answers/2d-arrays-in-c), [lists](https://www.educative.io/answers/what-is-a-linked-list), [stacks](https://www.educative.io/answers/what-is-a-stack), etc.

To use the STL stack, you must first include the stack file:

```c++
#include <stack>
```

Next, declare an object of type `stack` and specify the type of elements it will contain using the [C++ template](https://www.educative.io/answers/what-are-class-templates-in-c) syntax.

STL provides the following methods that are​ (usually) associated with a stack:

1. **`push(e)`**: Places the element passed as the parameter (`e`) on top of the stack.

2. **`pop()`**: Returns the top-most element of the stack and removes it.

3. **`top()`**: Returns the top-most element of the stack without removing it.

4. **`size()`**: Returns the total number of elements in the stack.

5. **`empty()`**: Returns `true`, if the stack is empty, and `false` if otherwise.

# Demo

A stack follows the last-in-first-out (LIFO) principle (i.e., the last element added to the stack is the first to be removed​).

#include <iostream>
#include <stack>

using namespace std;

int main(){
    stack<int> s;

    // Push elements on the stack:
    s.push(3);
    s.push(5);
    s.push(7);
    
    // Empty the whole stack:
    while(!s.empty()){
        // Print info:
        cout << "top() -> " << s.top() << endl
        << "size() -> " << s.size() << endl << endl;
        
        // Pop out the top element:
        s.pop(); // Can be stored in a variable
    }
}


How to use the STL stack in C++

Demo

Code