Stack in C++ STL - GeeksforGeeks

Stacks are a type of container adaptors with LIFO(Last In First Out) type of working, where a new element is added at one end and (top) an element is removed from that end only.

The functions associated with stack are:
empty() – Returns whether the stack is empty – Time Complexity : O(1)
size() – Returns the size of the stack – Time Complexity : O(1)
top() – Returns a reference to the top most element of the stack – Time Complexity : O(1)
push(g) – Adds the element ‘g’ at the top of the stack – Time Complexity : O(1)
pop() – Deletes the top most element of the stack – Time Complexity : O(1)

// CPP program to demonstrate working of STL stack 
#include <iostream> 
#include <stack> 
using namespace std; 
  
void showstack(stack <int> s) 
{ 
    while (!s.empty()) 
    { 
        cout << '\t' << s.top(); 
        s.pop(); 
    } 
    cout << '\n'; 
} 
  
int main () 
{ 
    stack <int> s; 
    s.push(10); 
    s.push(30); 
    s.push(20); 
    s.push(5); 
    s.push(1); 
  
    cout << "The stack is : "; 
    showstack(s); 
  
    cout << "\ns.size() : " << s.size(); 
    cout << "\ns.top() : " << s.top(); 
  
  
    cout << "\ns.pop() : "; 
    s.pop(); 
    showstack(s); 
  
    return 0; 
} 

Output:

The stack is :     1    5    20    30    10

s.size() : 5
s.top() : 1
s.pop() :     5    20    30    10

List of functions of Stack:

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