Merge pull request #361 from Arisha2902/main

create doubly linked list FIX #255

DSA SOLUTIONS (TILL TREE & BASIC GRAPH CONCEPTS)/doublyLinkedList.c

@@ -0,0 +1,157 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct list {
+    int data;
+    struct list *next;
+    struct list *prev;
+} *head = NULL, *tail = NULL;
+
+void init() {
+    head = NULL;
+    tail = NULL;
+}
+
+void print() {
+    struct list *temp = head;
+    while (temp != NULL) {
+        printf("%d ", temp->data);
+        temp = temp->next;
+    }
+    printf("\n");
+}
+
+void linkedlist_start(int val) {
+    struct list *p = (struct list *)malloc(sizeof(struct list));
+    p->data = val;
+    p->next = head;
+    p->prev = NULL;
+    if (head != NULL) {
+        head->prev = p;
+    } else {
+        tail = p;
+    }
+    head = p;
+}
+
+void linkedlist_end(int val) {
+    struct list *p = (struct list *)malloc(sizeof(struct list));
+    p->data = val;
+    p->next = NULL;
+    if (tail != NULL) {
+        tail->next = p;
+        p->prev = tail;
+    } else {
+        head = p;
+    }
+    tail = p;
+}
+
+void linkedlist_k(int val, int k) {
+    struct list *p = (struct list *)malloc(sizeof(struct list));
+    p->data = val;
+    if (k == 1) {
+        linkedlist_start(val);
+    } else if (k == 2) {
+        linkedlist_end(val);
+    } else {
+        struct list *temp = head;
+        for (int i = 1; i < k - 1 && temp->next != NULL; i++) {
+            temp = temp->next;
+        }
+        if (temp->next == NULL) {
+            temp->next = p;
+            p->prev = temp;
+            p->next = NULL;
+            tail = p;
+        } else {
+            p->next = temp->next;
+            p->prev = temp;
+            temp->next->prev = p;
+            temp->next = p;
+        }
+    }
+}
+
+void del(int k) {
+    struct list *temp;
+    if (head == NULL) {
+        printf("List is empty\n");
+        return;
+    } else if (k == 1) {
+        temp = head;
+        if (head->next == NULL) {
+            head = NULL;
+        } else {
+            head = head->next;
+            head->prev = NULL;
+        }
+        printf("%d deleted\n", temp->data);
+        free(temp);
+    } else {
+        temp = head;
+        for (int i = 1; i < k - 1 && temp->next != NULL; i++) {
+            temp = temp->next;
+        }
+        if (temp->next != NULL) {
+            temp->next->prev = temp->prev;
+            temp->prev->next = temp->next;
+        } else {
+            temp->prev->next = NULL;
+        }
+        printf("%d deleted\n", temp->data);
+        free(temp);
+    }
+}
+
+void menu() {
+    int choice, val, k;
+    while (1) {
+        printf("Menu:\n");
+        printf("1. Insert at start\n");
+        printf("2. Insert at end\n");
+        printf("3. Insert at position k\n");
+        printf("4. Print the list\n");
+        printf("5. Delete a node\n");
+        printf("6. Exit\n");
+        printf("Enter your choice: ");
+        scanf("%d", &choice);
+        switch (choice) {
+            case 1:
+                printf("Enter value: ");
+                scanf("%d", &val);
+                linkedlist_start(val);
+                break;
+            case 2:
+                printf("Enter value: ");
+                scanf("%d", &val);
+                linkedlist_end(val);
+                break;
+            case 3:
+                printf("Enter value: ");
+                scanf("%d", &val);
+                printf("Enter position: ");
+                scanf("%d", &k);
+                linkedlist_k(val, k);
+                break;
+            case 4:
+                print();
+                break;
+            case 5:
+                printf("Enter position to delete: ");
+                scanf("%d", &k);
+                del(k);
+                break;
+            case 6:
+                exit(0);
+            default:
+                printf("Invalid choice\n");
+        }
+    }
+}
+
+int main() {
+    init();
+    menu();
+    return 0;
+}