stack-linked-list.cpp

/* Program to implement stacks as linked lists */

#include<iostream>
#include<conio.h>
#include<process.h>

using namespace std;

struct node {
	int roll;
	node* next;
} *top, *save, *ptr, *newptr, *np;

node *create(int a) {
	ptr=new node;
	ptr->roll=a;
	ptr->next=NULL;
	return ptr;
}

void push(node *np) {
	if (top==NULL) {
		top=np;
	}
	else {
		save=top;
		top=np;
		np->next=save;
	}
}

void pop() {
	if (top==NULL) {
		cout<<"Underflow";
	}
	else {
		ptr=top;
		top=top->next;
		delete ptr;
	}
}

void display(node *np){
	while (np!=NULL) {
		cout<<np->roll<<"->";
		np=np->next;
	}
}

int main () {
	top=NULL;
	int m, n;
	char k, ch;
	do {
		cout<<"\nChoose from the menu: ";
		cout<<"\n 1. Push";
		cout<<"\n 2. Pop";
		cout<<"\n 3. Display";
		cout<<"\n 4. Quit";
		cout<<endl<<"Enter your choice (1..4): ";
		cin>>n;
		switch(n) {
			case 1: k='y';
			while (k=='y' || k=='Y') {
				cout<<"Enter element to be inserted: ";
				cin>>m;
				newptr=create(m);
				if (newptr==NULL) {
					cout<<"\n Cannot create!!";
				}
				else 
					push(newptr);
					cout<<"\n The stack formed is: ";
					display(top);
					cout<<"\n Want to enter again ? ";
					cin>>k;
				}
				break;
			case 2: k='y';
			while (k=='y' || k=='Y') {
				pop();
				cout<<"\n The stack formed is: ";
				display(top);
				cout<<"\n Want to delete again ? ";
				cin>>k;
			}
			break;
			case 3: cout<<"\n The stack formed is: ";
					display(top);
					break;
			case 4: exit(0);
					break;
			default: cout<<"\n Please enter desired keyword: ";
		}	
		cout<<"\n Do you want to continue ? ";
		cin>>ch;
	} while (ch=='y' || ch=='Y');
	getch();
	return 0;
}