Linked List

 

#include <stdio.h>
#include <stdlib.h>

struct NODE {
	int ID;
	int value;
	struct NODE* next;
}*head, *tail, *ptr;

void L_input();
void L_print();
void L_update();
void L_delete();

int main(void) {
	head = NULL;
	int index, flag = 0;
	while (flag == 0) {
		printf("Enter [(1) Input, (2) Print, (3) Update, (4) Delete, (5) Exit]: ");
		scanf_s("%d", &index);
		if (index == 1) { L_input(); }
		else if (index == 2) { L_print(); }
		else if (index == 3) { L_update(); }
		else if (index == 4) { L_delete(); }
		else if (index == 5) { printf("Exit this Program\n"); flag == 1; }
		else { printf("Enter Again (between 1 and 5)\n"); }
	}
	return 0;
}

void L_input()
{
	int in_ID, in_value;
	printf("\tID, value : ");
	scanf_s("%d %d", &in_ID, &in_value);
	ptr = (struct NODE*)malloc(sizeof(struct NODE));
	if (head == NULL) { head = ptr; } else { tail->next = ptr; }
	ptr->ID = in_ID;
	ptr->value = in_value;
	ptr->next = NULL;
	tail = ptr;
	L_print();
}

void L_print()
{
	ptr = head;
	printf("(ID, Values) : ");
	while (ptr != NULL) {
		printf("(%d, %d)", ptr->ID, ptr->value);
		ptr = ptr->next;
	}
	printf("\n");
}

void L_update()
{
	int update_ID, update_value;
	printf("\tID for update: "); scanf_s("%d", &update_ID);
	ptr = head;
	while (ptr != NULL) {
		if (ptr->ID == update_ID) {
			printf("\tEnter the value for this ID: ");
			scanf_s("%d", &update_value);
			ptr->value = update_value;
			L_print();
			return;
		}
		ptr = ptr->next;
	}
}

void L_delete()
{
	int delete_ID;
	printf("\tID for delete: "); scanf_s("%d", &delete_ID);
	ptr = head;
	if (ptr->ID == delete_ID); {	/* Delete the first NODE */
		head = ptr->next;
		free(ptr);
		L_print();
		return;
	}
	struct NODE* tmp;
	while (ptr != NULL) { /* Otherwise */ 
		tail = ptr;
		ptr = ptr->next;
		if (ptr->ID == delete_ID) {
			tail->next = ptr->next;
			tmp = tail;
			free(ptr);
			while (tail->next != NULL) {
				tail = tmp;
				tmp = tmp->next;
			}
			L_print();
			return;
		}
	}
}