Program 14 - Linked List Operations

	#include <stdio.h>
	#include <stdlib.h>
	struct node{
	int data;
	struct node *next;
	};
	struct node *start = NULL, *last = NULL;
	void create(){
	int num;
	struct node *nn;
	printf("Enter data: ");
	scanf("%d", &num);
	while(num != -1){
	nn = (struct node *)malloc(sizeof(struct node));
	nn -> data = num;
	nn -> next = NULL;
	if(start == NULL){
	start = nn;
	last = nn;
	} else {
	last -> next = nn;
	last = nn;
	}
	printf("Enter data or enter -1 to stop: ");
	scanf("%d", &num);
	}
	}
	void insert_end(int num){
	struct node *nn;
	if(start == NULL){
	printf("Empty Linked List\n");
	} else {
	nn = (struct node *)malloc(sizeof(struct node));
	nn -> data = num;
	nn -> next = NULL;
	last -> next = nn;
	last = nn;
	display();
	}
	}
	void delete_end(){
	struct node *prev = NULL, *delete_this;
	int num;
	if(start == NULL){
	printf("Empty Linked List\n");
	} else if(start -> next == NULL){
	// Only one node
	printf("%d deleted from Linked List\n", start -> data);
	free(start);
	free(last);
	start = last = NULL;
	display();
	} else {
	delete_this = start;
	while(delete_this -> next != NULL){
	prev = delete_this;
	delete_this = delete_this -> next;
	}
	/* Now delete_this is at last position
	* and prev is at second last position
	*/
	prev -> next = NULL;
	last = prev;
	printf("%d deleted from Linked List\n", delete_this -> data);
	free(delete_this);
	display();
	}
	}
	void display(){
	struct node *p;
	if(start == NULL){
	printf("Empty Linked list\n");
	} else {
	p = start;
	while(p != NULL){
	printf("%d ->", p -> data);
	p = p -> next;
	}
	printf("NULL\n");
	}
	}
	int main(){
	int choice, rpt = 1, num;
	printf("***Create Linked List***\n");
	create();
	system("cls");
	while(rpt != 0){
	display();
	printf("1. Insert at end\n2. Delete at end\n3. Display\n4. Exit\n");
	printf("--------------\n");
	printf("Enter a choice: ");
	scanf("%d", &choice);
	switch(choice){
	case 1:
	printf("Enter num: ");
	scanf("%d", &num);
	insert_end(num);
	break;
	case 2:
	delete_end();
	break;
	case 3:
	display();
	break;
	case 4:
	exit(0);
	}
	printf("Do you want to continue? (1/0): ");
	scanf("%d", &rpt);
	system("cls");
	}
	}