DS3_1

#include <iostream.h> #include <conio.h> #include <stdlib.h> struct list { int data; struct list *prev,*next; }*top; int push(); int pop(); int peep(); int change(); void main() { int choice; while(1) { clrscr(); cout<<"\nSTACK OPERATIONS :\n"; cout<<"1. Push\n2. Pop\n3. Peep\n4. Change"; cout<<"\n5. Exit\nEnter choice : "; cin>>choice; switch(choice) { case 1: push(); break; case 2: pop(); break; case 3: peep(); break; case 4: change(); break; default: exit(0); } } } int push() { if(top==NULL) { top=(struct list *)malloc(sizeof(struct list)); top->prev=NULL; } else { top->next=(struct list *)malloc(sizeof(struct list)); top->next->prev=top; top=top->next; } cout<<"\n\nPUSH :\nEnter data : "; cin>>top->data; return 0; } int pop() { if(top==NULL) { cout<<"\nStack empty!"; getch(); return 0; } top=top->prev; free(top->next); cout<<"\n\nPOP :\nData popped."; getch(); return 0; } int peep() { if(top==NULL) { cout<<"\nStack empty!"; getch(); return 0; } cout<<"\n\nPEEP :\n"<<top->data; getch(); return 0; } int change() { if(top==NULL) { cout<<"\nStack empty!"; getch(); return 0; } cout<<"\n\nCHANGE :\n"; cout<<"Current data : "<<top->data; cout<<"\nEnter new data : "; cin>>top->data; cout<<"\nData changed."; getch(); return 0; }