Linked List in js

Author: nb-0310

Linked List/linked_list.js

@@ -0,0 +1,226 @@
+/* 
+    insertAtTail (val)
+    insertAtHead (val)
+    deleteAtTail ()
+    deleteAtHead ()
+    getLength ()
+    print ()
+    getAtIdx (idx)
+    putAtIdx (val, idx)
+    deleteAtIdx (idx)
+    search (val)
+    toArray ()
+    reverse ()
+*/
+
+class Node {
+    constructor(val) {
+        this.val = val
+        this.next = null
+    }
+}
+
+class LinkedList {
+    constructor() {
+        this.head = null
+        this.tail = null
+        this.length = 0
+    }
+
+    insertAtTail(val) {
+        const node = new Node(val)
+
+        if (!this.head) {
+            this.head = node
+            this.tail = node
+            this.length++
+        } else {
+            this.tail.next = node
+            this.tail = node
+            this.length++
+        }
+    }
+
+    insertAtHead(val) {
+        const node = new Node(val)
+
+        if (!this.head) {
+            this.head = node
+            this.tail = node
+            this.length++
+        } else {
+            node.next = this.head
+            this.head = node
+            this.length++
+        }
+    }
+
+    print() {
+        if (this.length === 0) console.log ("Empty Linked List!")
+        else {
+            let curr = this.head
+            let str = ''
+
+            while (curr) {
+                str += curr.val + ' -> '
+                curr = curr.next
+            }
+
+            console.log(str + 'null')
+        }
+    }
+
+    deleteAtTail() {
+        if (!this.head) console.log("Empty Linked List!")
+
+        else {
+            let curr = this.head
+            let prev = this.head
+
+            while (curr.next) {
+                prev = curr
+                curr = curr.next
+            }
+
+            prev.next = null
+            this.tail = prev
+            this.length--
+        }
+    }
+
+    deleteAtHead() {
+        if (!this.head) console.log("Empty Linked List!")
+
+        else {
+            let curr = this.head
+            this.head = curr.next
+            this.length--
+        }
+    }
+
+
+    getLength() {
+        return this.length
+    }
+
+    getAtIdx (idx) {
+        if (idx >= this.length || idx < 0) throw new Error ("Index out of bounds")
+
+        else {
+            let currIdx = 0
+            let curr = this.head
+
+            while (currIdx < idx) {
+                currIdx++
+                curr = curr.next
+            }
+
+            return curr.val
+        } 
+    }
+
+    putAtIdx (val, idx) {
+        if (idx > this.length || idx < 0) throw new Error ("Index out of bounds")
+
+        const node = new Node (val)
+
+        if (!this.head) {
+            this.head = node
+            this.length++
+            return
+        }
+
+        let currIdx = 0
+        let curr = this.head
+        let prev = this.head
+
+        while (currIdx < idx) {
+            currIdx++
+            prev = curr
+            curr = curr.next
+        }
+
+        prev.next = node
+        node.next = curr
+        this.length++
+    }
+
+    deleteAtIdx (idx) {
+        if (idx >= this.length || idx < 0) throw new Error ("Index out of bounds")
+
+        else {
+            let currIdx = 0
+            let curr = this.head
+            let prev = this.head
+
+            while (currIdx < idx) {
+                currIdx++
+                prev = curr
+                curr = curr.next
+            }
+
+            prev.next = curr.next
+            this.length--
+        }
+    }
+
+    search (val) {
+        if (!this.head) return "Empty Linked List!"
+        if (!this.head.next && this.head.val !== val) return null
+        if (!this.head.next && this.head.val === val) return 0
+        
+        let currIdx = 0
+        let curr = this.head
+
+        while (curr) {
+            if (curr.val === val) return currIdx
+            currIdx++
+            curr = curr.next
+        }
+
+        return null
+    }
+
+    toArray () {
+        const arr = []
+        if (!this.head) return null
+
+        let curr = this.head
+
+        while (curr) {
+            arr.push (curr.val)
+            curr = curr.next
+        }
+
+        return arr
+    }
+
+    reverse () {
+        if (!this.head) throw new Error ("Empty Linked List")
+        if (!this.head.next) return
+
+        let prev = null
+        let curr = this.head
+        let next = curr.next
+
+        while (curr) {
+            next = curr.next
+            curr.next = prev
+            prev = curr
+            curr = next
+        }
+
+        this.head = prev
+    }
+}
+
+// SAMPLE USECASE
+
+const list = new LinkedList()
+list.insertAtTail (10)
+list.insertAtTail (20)
+list.insertAtTail (30)
+list.insertAtTail (40)
+list.insertAtTail (50)
+list.reverse ()
+list.print ()