C++ Program to Implement Stack

In this program we will see how to implement stack using C++. A stack is an abstract data structure that contains a collection of elements. Stack implements the LIFO mechanism i.e. the element that is pushed at the end is popped out first. Some of the principle operations in the stack are −

• Push - This adds a data value to the top of the stack.

• Pop - This removes the data value on top of the stack

• Peek - This returns the top data value of the stack

A program that implements a stack using array is given as follows.

Input: Push elements 11, 22, 33, 44, 55, 66
Output: Pop elements 66, 55, 44, 33, 22, 11

Algorithm

push(item)

Begin
   increase the top pointer by 1
   insert item into the location top
End

pop()

Begin
   item = top element from stack
   reduce top pointer by 1
   return item
End

peek()

Begin
   item = top element from stack
   return item
End

Example Code

#include <iostream>
using namespace std;
int stack[100], n = 100, top = -1;
void push(int val) {
   if(top >= n-1)
      cout<<"Stack Overflow"<<endl;
   else {
      top++;
      stack[top] = val;
   }
}
void pop() {
   if(top <= -1)
      cout<<"Stack Underflow"<<endl;
   else {
      cout<<"The popped element is "<< stack[top] <<endl;
      top--;
   }
}
void display() {
   if(top>= 0) {
      cout<<"Stack elements are:";
      for(int i = top; i>= 0; i--)
         cout<<stack[i]<<" ";
      cout<<endl;
   } else
      cout<<"Stack is empty";
}
int main() {
   int ch, val;
   cout<<"1) Push in stack"<<endl;
   cout<<"2) Pop from stack"<<endl;
   cout<<"3) Display stack"<<endl;
   cout<<"4) Exit"<<endl;
   do {
      cout<<"Enter choice: "<<endl;
      cin>>ch;
      switch(ch) {
         case 1: {
            cout<<"Enter value to be pushed:"<<endl;
            cin>>val;
            push(val);
            break;
         }
         case 2: {
            pop();
            break;
         }
         case 3: {
            display();
            break;
         }
         case 4: {
            cout<<"Exit"<<endl;
            break;
         }
         default: {
            cout<<"Invalid Choice"<<endl;
         }
      }
   }while(ch! = 4);
   return 0;
}

Output

1) Push in stack
2) Pop from stack
3) Display stack
4) Exit

Enter choice: 1
Enter value to be pushed: 2
Enter choice: 1
Enter value to be pushed: 6
Enter choice: 1
Enter value to be pushed: 8
Enter choice: 1
Enter value to be pushed: 7
Enter choice: 2
The popped element is 7
Enter choice: 3
Stack elements are:8 6 2
Enter choice: 5
Invalid Choice
Enter choice: 4
Exit