Data structures: implement doubly linked list - insert and remove at K index

Author: ChauDinh

Data Structures/Linked Lists/doubleLinkedList.js

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+/**
+ * Doubly Linked List implement with JavaScript
+ */
+
+// Initialize a node
+
+class Node {
+  constructor(data, prev = null, next = null) {
+    this.data = data;
+    this.prev = prev;
+    this.next = next;
+  }
+}
+
+class DoublyLinkedList {
+  constructor() {
+    this.head = null;
+    this.tail = null;
+    this.size = 0;
+  }
+
+  // Search first node with key K
+  searchFirstNode(data) {
+    if (!this.head) return null;
+    let current = this.head;
+    while (current !== null && current.data !== data) {
+      current = current.next;
+    }
+
+    return current;
+  }
+
+  // Insert Node at index
+  insert(data, index) {
+    // If index is out of range
+    if (index > 0 && index > this.size) return;
+    let node = new Node(data);
+
+    // If index = 0: insert at head
+    if (index === 0) {
+      if (!this.head) {
+        this.head = node;
+        this.tail = node;
+        this.size++;
+      } else {
+        let current = this.head;
+        node.next = current;
+        current.prev = node;
+        this.head = node;
+        this.size++;
+      }
+    } else if (index === this.size) {
+      let current = this.tail;
+      node.prev = current;
+      current.next = node;
+      this.tail = node;
+      this.size++;
+    } else {
+      // Insert at given index k
+      let counter = 0;
+      let current = this.head;
+      while (counter < index) {
+        current = current.next;
+        counter++;
+      }
+      node.next = current;
+      current.prev.next = node;
+      node.prev = current.prev;
+      this.size++;
+    }
+  }
+
+  // Remove a node at given K index
+  remove(index) {
+    if (index > 0 && index > this.size) return;
+
+    // index = 0: Remove the head node
+    if (index === 0) {
+      if (!this.head) return;
+      else {
+        this.head = this.head.next;
+        this.head.prev = null;
+        this.size--;
+      }
+    } else if (index === this.size - 1) {
+      this.tail = this.tail.prev;
+      this.tail.next = null;
+      this.size--;
+    } else {
+      let counter = 0;
+      let current = this.head;
+      while (counter < index) {
+        current = current.next;
+        counter++;
+      }
+      current.prev.next = current.next;
+      current.next.prev = current.prev;
+      this.size--;
+    }
+  }
+}
+
+const dbl = new DoublyLinkedList();
+
+dbl.insert(100, 0);
+dbl.insert(200, 0);
+dbl.insert(400, 0);
+dbl.insert(300, 1);
+dbl.insert(500, 3);
+dbl.remove(1);
+
+console.log(dbl);