DATA STRUCTURE AND ALGORITHM (Stack)

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STACK

 

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 (top) and an element is removed from that end only. 


Stack


Stack Syntax:-
template <class Type, class Container = deque<Type> > class stack;

 Type – is the Type of element contained in the std::stack. It can be any valid C++ type or even a user-defined type.

Container – is the Type of underlying container object.



Member Types:-

  • value_type- The first template parameter, T. It denotes the element types.
  • container_type- The second template parameter, Container. It denotes the underlying container type.
  • size_type- Unsigned integral type.
  
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) 


A simple CPP program to introduce a stack:

#include <iostream>
#include <stack>
using namespace std;

int main() 
{
 stack<int> stack;
 stack.push(6);
 stack.push(24);
 stack.push(4);
 stack.push(5);
stack.pop();          // deletes 5
 stack.pop();          // deletes 4

 while (!stack.empty()) {
 cout << ' ' << stack.top();
 stack.pop();
 }

        return 0;
}

Output
 6 24
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