Stack

A stack is a linear data structure in which follows a particular order in which the operations are performed. The insertion and deletion of elements are performed in Last in First out (LIFO) order or First in Last out (FILO) order. We can say that the insertion and deletion can be done at one end only.

There are many real-life examples of a stack. For example, the plates are stacked over another in the canteen. The plate which is at the top is the first one to be removed which means the plate which is at the bottom most position remains in the stack for the longest period of time.

Basic Operations of Stack

The following are the basic operations performed in the stack:

Push: Adds an item to the stack. If the stack is full, then it is said to be an Overflow condition.

Pop: Removes an item from the stack. The items are popped in the reverse order in which they are pushed. If the stack is empty, then it is said to be an Underflow condition.

Top: Returns top element of stack.

 isEmpty: Return true if stack is empty, else false.

The following are the various operations of Stack:

• Initialize the stack to be empty
• Determine whether the stack is empty or not
• Check whether the stack is full or not
• If the stack is not full, add or insert a new node at the top of the stack. This operation is termed as Push operation.
• If the stack is not empty, then retrieve the node at its top
• If the stack is not empty, then we could delete the node at the top. This operation is termed as Pop operation.

#include <stdio.h>
#include<stdlib.h>

int top = -1;
int stk[5];

void push(int x)
{
    if(top > 4)
    {
        printf("Stack overflow");
        return;
    }

    stk[++top] = x;
    printf("Inserted the value %d\n", x);
}

void pop()
{
    if(top < 0)
    {
        printf("Stack underflow");
        return;
    }
    printf("The deleted element is %d\n", stk[top--]);
}

void display()
{
    if (top < 0)
    {
        printf("Stack is empty\n");
        return;
    }
    for (int i = top; i >= 0; i--)
    {
        printf("%d\t", stk[i]);
    }
}


int main()
{
    int ch;
    int val;
    while (1) {
        printf("\n1.push 2.pop 3.display 4.exit\nEnter ur choice: ");
        scanf("%d", &ch);
        switch (ch) {
        case 1:
            printf("Enter the element: ");
            scanf("%d", &val);
            push(val);
            break;
        case 2:
            pop();
            break;
        case 3:
            display();
            break;
        case 4:
            exit(0);
        }
    }
}

1.push 2.pop 3.display 4.exit
Enter ur choice: 1
Enter the element: 5
Inserted the value 5

1.push 2.pop 3.display 4.exit
Enter ur choice: 1
Enter the element: 10
Inserted the value 10

1.push 2.pop 3.display 4.exit
Enter ur choice: 1
Enter the element: 15
Inserted the value 15

1.push 2.pop 3.display 4.exit
Enter ur choice: 2
The deleted element is 15

1.push 2.pop 3.display 4.exit
Enter ur choice: 3
10      5
1.push 2.pop 3.display 4.exit

#include<stdio.h>
#include<stdlib.h>
struct node
{
    int data;
    struct node *link;
}*top;

void push(int x)
{
    struct node *temp;
    temp=(struct node *)malloc(sizeof(struct node));
    temp->data=x;
    temp->link=top;
    top=temp;
}

void pop()
{
    struct node *temp;
    if(top==NULL)
    {
        printf("Stack is empty");
        return;
    }
    temp=top;
    top=top->link;
    free(temp);
}

void print()
{
    struct node *temp=top;
    while(temp!=NULL)
    {
        printf("%d\t",temp->data);
        temp=temp->link;
    }
    printf("\n");
}

void main()
{
    push(2);
    push(3);
    push(6);
    print();
    printf("Pop the top element\n");
    pop();
    printf("Push 10 to the stack\n");
    push(10);
    print();
}

6       3       2
Pop the top element
Push 10 to the stack
10      3       2