1// Aim: Program to perform Circular Linked List operations (Insertion, Deletion).
2#include<stdio.h>
3#include<stdlib.h>
4
5struct node {
6    int data;
7    struct node *link;
8};
9
10struct node *head = NULL;
11
12void insertfront(int x){
13    struct node *new = (struct node *)malloc(sizeof(struct node));
14    new->data = x;
15    if(head == NULL){
16        head = new;
17        new->link = head;
18    }else{
19        struct node *ptr = head;
20        while(ptr->link != head){
21            ptr = ptr->link;
22        }
23        ptr->link = new;
24        new->link = head;
25        head = new;
26    }
27}
28
29void insertend(int x){
30    struct node *new = (struct node *)malloc(sizeof(struct node));
31    new->data = x;
32    if(head == NULL){
33        head = new;
34        new->link = head;
35    }else{
36        struct node *ptr = head;
37        while(ptr->link != head){
38            ptr = ptr->link;
39        }
40        ptr->link = new;
41        new->link = head;
42    }
43}
44
45void insertafter(int key, int x){
46    if(head == NULL){
47        printf("List is empty\n");
48    }
49    else{
50        struct node *ptr = head;
51        while(ptr->link != head && ptr->data != key){
52            ptr = ptr->link;
53            if(ptr == head){
54                break;
55            }
56        }
57        if(ptr->data == key){
58            struct node *new = (struct node *)malloc(sizeof(struct node));
59            new->data = x;
60            new->link = ptr->link;
61            ptr->link = new;
62        }else{
63            printf("Key not found\n");
64        }
65    }
66}
67
68void deletefront(){
69    if(head == NULL){
70        printf("List is empty\n");
71    }else if(head->link == head){
72        struct node *temp = head;
73        head = NULL;
74        free(temp);
75    }else{
76        struct node *ptr = head;
77        struct node *temp = head;
78        while(ptr->link != head){
79            ptr = ptr->link;
80        }
81        head = head->link;
82        ptr->link = head;
83        free(temp);
84    }
85}
86
87void deleteend(){
88    if(head == NULL){
89        printf("List is empty\n");
90    }else if(head->link == head){
91        struct node *temp = head;
92        head = NULL;
93        free(temp);
94    }else{
95        struct node *prev = head;
96        struct node *curr = head->link;
97        while(curr->link != head){
98            prev = curr;
99            curr = curr->link;
100        }
101        prev->link = head;
102        free(curr);
103    }
104}
105
106void deletekey(int key){
107    if(head == NULL){
108        printf("List is empty\n");
109    }else if(head->link == head){
110        if(head->data == key){
111            struct node *temp = head;
112            head = NULL;
113            free(temp);
114        }else{
115            printf("Key not found\n");
116        }
117    }else if(head->data == key){
118        struct node *ptr = head;
119        struct node *temp = head;
120        while(ptr->link != head){
121            ptr = ptr->link;
122        }
123        head = head->link;
124        ptr->link = head;
125        free(temp);
126    }else{
127        struct node *prev = head;
128        struct node *curr = head->link;
129        while(curr != head && curr->data != key){
130            prev = curr;
131            curr = curr->link;
132        }
133        if(curr->data == key){
134            prev->link = curr->link;
135            free(curr);
136        }else{
137            printf("Key not found\n");
138        }
139    }
140}
141
142void display(){
143    if(head == NULL){
144        printf("List is empty\n");
145    }else{
146        struct node *ptr = head;
147        do{
148            printf("%d ", ptr->data);
149            ptr = ptr->link;
150        }while(ptr != head);
151        printf("\n");
152    }
153}
154
155void main(){
156    int ch, x, key;
157    while(1){
158        printf("1. Insert front\n");
159        printf("2. Insert end\n");
160        printf("3. Insert after\n");
161        printf("4. Delete front\n");
162        printf("5. Delete end\n");
163        printf("6. Delete key\n");
164        printf("7. Display\n");
165        printf("8. Exit\n");
166        printf("Enter your choice: ");
167        scanf("%d", &ch);
168        switch(ch){
169            case 1:
170                printf("Enter the element to insert: ");
171                scanf("%d", &x);
172                insertfront(x);
173                break;
174            case 2:
175                printf("Enter the element to insert: ");
176                scanf("%d", &x);
177                insertend(x);
178                break;
179            case 3:
180                printf("Enter the key: ");
181                scanf("%d", &key);
182                printf("Enter the element to insert: ");
183                scanf("%d", &x);
184                insertafter(key, x);
185                break;
186            case 4:
187                deletefront();
188                break;
189            case 5:
190                deleteend();
191                break;
192            case 6:
193                printf("Enter the key: ");
194                scanf("%d", &key);
195                deletekey(key);
196                break;
197            case 7:
198                display();
199                break;
200            case 8:
201                exit(0);
202            default:
203                printf("Invalid choice\n");
204        }
205    }
206}
207