[gobicse]

Program to illustrate stack using Linked list concept:

/*Program to illustrate stack using linked list concept*/
#include /*Link section*/
struct node /*Structure used to represent elements as nodes*/
{
int val; /*Element*/
struct node *next; /*Next pointer*/
}*top = NULL,*temp = NULL;
void push(int); /*Function declaration section*/
int pop();
void disp();

/*Main function starts here*/
void main()
{
int opt,item,popped;
/*Loop which processes infinitely and ends when forced by the user*/
do
{
clrscr();
printf("Enter the required option\n1.Push\n2.Pop\n3.View the stack\n4.exit:");
scanf("%d",&opt); /*Option is received here*/
switch(opt)
{
case 1:
printf("Enter the element to push:");
scanf("%d",&item);
push(item); /*Element pushed into the stack*/
break;

case 2:
popped = pop(); /*Element popped out of the stack*/
if(popped == 0)
{
disp();
continue;
}
printf("Popped element = %d",popped);
getch();
break;

case 3:
disp(); /*Used to diplay the stack*/
break;
}
}while(opt != 4);
}

/*Function to push an element into the stack*/
void push(int item)
{
if(top == NULL) /*Condition which checks whether first element*/
{
/*Reserving memory space using malloc*/
top = (struct node *)malloc(sizeof(struct node));

/*Assigning the first element as the entered value*/
top->val = item;

/*Assigning the next pointer to NULL*/
top->next = NULL;
}
else
{
/*Reserving memory space using malloc*/
temp = (struct node *)malloc(sizeof(struct node));

/*Asssigning the entered value into a temporary space*/
temp->val = item;

/*Mapping the next pointer to the previous element*/
temp->next = top;

/*Mapping the top of stack with the current element*/
top = temp;
}
}



int pop()
{
int res;
if(top == NULL) /*Checking for the stack to be empty*/
return(0);
else
{
int pop;
pop = top->val; /*Storing the popped value into a variable*/
temp = top;

/*Manipulating the pointers to remove the element*/
top = top->next;
free(temp); /*Making the temporary space free*/
return pop; /*Returning the value stored to pop out*/
}
}

void disp()
{
if(top == NULL) /*Condition checking for the stack to be empty*/
{
printf("The stack is empty");
getch();
return;
}
temp = top;
printf("The stack elements are:\n");
while(temp != NULL) /*Printing the stack elements*/
{
printf("\n%d",temp->val);

/*Moving the temporary pointer to the next element*/
temp = temp->next;
}
getch();
}




Output:

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:3
The stack is empty

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:1
Enter the element to push:156

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:1
Enter the element to push:185

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:1
Enter the element to push:894

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:1
Enter the element to push:474




Enter the required option
1.Push
2.Pop
3.View the stack
4.exit3
The stack elements are:

474
894
185
156

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:2
Popped element = 474

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:2
Popped element = 894

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:3
The stack elements are:

185
156





Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:2
Popped element = 185

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:2
Popped element = 156

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:2
The stack is empty

Enter the required option
1.Push
2.Pop
3.View the stack
4.exit:4