Data structure is a collection of data organised in a structured way. It is classified into two types which are linear data structure and non-linear data structure.
Linear data structure − Here, data is organised in a linear fashion.
For example − Arrays, structures, stacks, queues, linked lists.
Non-linear data structure − Here, Data is organised in a hierarchical way.
For example − Trees, graphs, sets, tables.
Stack in C language
It is a linear data structure, where data is inserted and removed only at one end.
Operations
- Push – Inserting an element into a stack.
- Pop – Deleting an element from a stack.
Deleted element = 50 Item = a [top] top --
- pop() ,pop(),pop(), pop()
Deleted element = 40 Deleted element=30 Deleted element=20 Deleted element =10
- Pop ( )
Stack under flow
Conditions
Stack over flow − Trying to insert an element into a full stack.
Stack under flow − Try to delete an element from a stack which is empty.
Algorithms for Push ( ), Pop ( ) , Display ( )
The respective algorithms are as follows −
Push ( )
- Check for stack overflow.
if (top = = n-1)
printf("stack over flow”);- Otherwise, insert an element into the stack.
top ++ a[top] = item
Pop ( )
- Check for stack underflow.
if ( top = = -1) printf( "stack under flow”);
- Otherwise, delete the element from the stack.
item = a[top] top --
Display ( )
- Check for stack flow.
if (top == -1)
printf ("stack is empty”);- Otherwise, follow the below mentioned algorithm −
for (i=0; i<top; i++)
printf ("%d”, a[i]);Example
Following is the C program for implementation of stack by using the arrays −
#include<stdio.h>
#include <conio.h>
int top = -1, n,a[100];
main ( ){
int ch;
void pop ( );
void display ( );
clrscr ( );
printf ("enter the size of the stack”);
scanf ("%d”, &n);
printf("stack implementation\n”);
printf ("1. push \n”);
printf ("2. Pop \n”);
printf ("3. exit \n”);
do{
printf ( "enter ur choice”);
scanf ("%d”, &ch);
switch (ch){
case 1 : push ( );
display ( );
break;
case 2 : push ( );
display ( );
break;
case 3 : exit
}
}while (ch>=1 | | ch<= 3);
getch ( );
}
void push ( ){
int item;
if (top = = n-1)
printf ( "stack over flow”)
else{
printf("enter an element for insertion”)
scanf ("%d”, &item);
top ++;
a[top] = item;
}
}
void pop ( ){
int item;
if (top = = -1);
printf ( "stack under flow”);
else{
item = a[top];
top --;
printf("deleted element = %d”, item);
}
}
void display ( ){
int i;
if (top = = -1)
printf ( "stack is empty”);
else{
printf("contents of the stack are”);
for (i=0; i<top; i++)
printf ("%d \t”, a[i]);
}
}Output
When the above program is executed, it produces the following result −
enter the size of the stack = 5 [given by user] Stack implementation 1. Push 2. Pop 3. exit Enter ur choice : 1 [given by user] Enter an element for insertion : 10 Contents of the stack : 10 Enter ur choice : 1 Enter an element for insertion : 2 Contents of the stack : 10 20 Enter ur choice : 2 Deleted element = 20 Contents of the stack are : 10 Enter ur choice : 2 Deleted element : 10 Contents of the stack are : stack is empty Enter ur choice : 2 Stack underflow. Enter ur choice : 1 Enter an element for insertion : 30 Contents of the stack are : 30