- A stack is a data structure that follows the Last In, First Out (LIFO) principle.
- It means that the last element added to the stack is the first one to be removed. Here’s a simple explanation with a diagram:
Stack Data Structure:
- A stack is like a collection of items stacked on top of each other. Think of it as a stack of books.
- You can only add or remove books from the top of the stack.
Operations:
- Push: Add an element to the top of the stack.
- Pop: Remove the element from the top of the stack.
- Peek (or Top): View the top element without removing it.
Diagram:
Let’s represent a stack with three elements (A, B, and C):
- Initially, the stack is empty.
- The element ‘A’ is pushed onto the stack.
- Then ‘B’ is pushed, and finally ‘C’ is pushed.
- The top of the stack is always the last element added (in this case, ‘C’).
- If we pop an element, ‘C’ will be removed first.
Operations:
-
Push ‘D’:
-
Pop:
- Peek (Top): (Without removing the top element) Simply displaying the top element
This diagram illustrates the basic idea of a stack. Elements are added to and removed from the top of the stack, and the top of the stack always represents the most recently added element.
STACK USING ARRAY
#include<stdio.h>
#include<stdlib.h>
int array[10];
int size = sizeof(array)/sizeof(array[0]);
int top = -1;
void push()
{
top++;
printf("Enter value tp insert:\n");
scanf("%d", &array[top]);
}
void pop()
{
top--;
}
void peek()
{
printf("The top: %d\n", array[top]);
}
void display()
{
printf("the list is:\n");
for(int i=0;i<=top;i++)
{
printf("%d\n", array[i]);
}
}
void isempty()
{
if(top==-1)
{
printf("empty!\n");
}
else
{
printf("Not empty!\n");
}
}
void isfull()
{
if(top>=size)
{
printf("FULL!\n");
}
else
{
printf("not full!\n");
}
}
int main()
{ int ch;
while(1)
{
printf("1.push\n2.pop\n3.peek\n4.display\n5.isempty\n6.isfull\n7.exit\n");
scanf("%d", &ch);
switch(ch)
{
case 1:
push();
break;
case 2:
pop();
break;
case 3:
peek();
break;
case 4:
display();
break;
case 5:
isempty();
break;
case 6:
isfull();
break;
case 7:
exit(0);
default:
printf("inavlid input!");
}
}
return 0;
}STACK USING LINKED LIST
#include <stdio.h>
#include <stdlib.h>
struct node
{
int data;
struct node *prev;
};
struct node *top = NULL;
void push()
{
struct node *newnode = (struct node *)malloc(sizeof(struct node));
printf("Enter the data:\n");
scanf("%d", &newnode->data);
if (top == NULL)
{
newnode->prev = NULL;
top = newnode;
}
else
{
newnode->prev = top;
// store the previous top in the prev part of the newnode
top = newnode;
// update the top aas the ADDRESS TO THE NEWNDODE
}
}
void display()
{
struct node *temp = top;
printf("The stack is:\n");
while (temp != NULL)
{
printf("%d, ", temp->data);
temp = temp->prev;
}
printf("\n");
}
void peep()
{
struct node *temp = top;
printf("The top is:\n");
printf("%d\n", temp->data);
}
void pop()
{
struct node *temp = top;
top = top->prev;
free(temp);
}
int main()
{
int ch;
while (1)
{
printf("1.push\n2.pop\n3.peek\n4.display\5.exit\n");
scanf("%d", &ch);
switch (ch)
{
case 1:
push();
break;
case 2:
pop();
break;
case 3:
peep();
break;
case 4:
display();
break;
case 5:
exit(0);
break;
default:
printf("wrong input!\n");
}
}
return 0;
}