stackLLImp.cpp

// C++ program to Implement a stack  
//using singly linked list  
#include <bits/stdc++.h>  
using namespace std;  
  
// Declare linked list node  
  
struct Node  
{  
    int data;  
    struct Node* link;  
};  
  
struct Node* top;  
  
// Utility function to add an element  
// data in the stack insert at the beginning  
void push(int data)  
{  
      
    // Create new node temp and allocate memory  
    struct Node* temp;  
    temp = new Node();  
  
    // Check if stack (heap) is full.  
    // Then inserting an element would  
    // lead to stack overflow  
    if (!temp) 
    {  
        cout << "\nHeap Overflow";  
        exit(1);  
    }  
  
    // Initialize data into temp data field  
    temp->data = data;  
  
    // Put top pointer reference into temp link  
    temp->link = top;  
  
    // Make temp as top of Stack  
    top = temp;  
}  
  
// Utility function to check if  
// the stack is empty or not  
int isEmpty()  
{  
    return top == NULL;  
}  
  
// Utility function to return top element in a stack  
int peek()  
{  
      
    // Check for empty stack  
    if (!isEmpty())  
        return top->data;  
    else
        exit(1);  
}  
  
// Utility function to pop top  
// element from the stack  
void pop()  
{  
    struct Node* temp;  
  
    // Check for stack underflow  
    if (top == NULL)  
    {  
        cout << "\nStack Underflow" << endl;  
        exit(1);  
    }  
    else
    {  
          
        // Top assign into temp  
        temp = top;  
  
        // Assign second node to top  
        top = top->link;  
  
        // Destroy connection between 
        // first and second  
        temp->link = NULL;  
  
        // Release memory of top node  
        free(temp);  
    }  
}  
  
// Function to print all the  
// elements of the stack  
void display()  
{  
    struct Node* temp;  
  
    // Check for stack underflow  
    if (top == NULL) 
    {  
        cout << "\nStack Underflow";  
        exit(1);  
    }  
    else 
    {  
        temp = top;  
        while (temp != NULL) 
        {  
  
            // Print node data  
            cout << temp->data << "-> ";  
  
            // Assign temp link to temp  
            temp = temp->link;  
        }  
    }  
}  
  
// Driver Code  
int main()  
{  
      
    // Push the elements of stack  
    push(11);  
    push(22);  
    push(33);  
    push(44);  
  
    // Display stack elements  
    display();  
  
    // Print top element of stack  
    cout << "\nTop element is "
         << peek() << endl;  
  
    // Delete top elements of stack  
    pop();  
    pop();  
  
    // Display stack elements  
    display();  
  
    // Print top element of stack  
    cout << "\nTop element is " 
         << peek() << endl;  
           
    return 0;  
}