From 912fd56a18f9659d3eb266af312b64ffead2606b Mon Sep 17 00:00:00 2001
From: Swastik Chugh <swastik.chugh@gdn-commerce.com>
Date: Thu, 1 Oct 2020 14:53:45 +0530
Subject: [PATCH] Circular linked list JavaScript implementation

---
 linked-list/circularLinkedList.js | 186 ++++++++++++++++++++++++++++++
 1 file changed, 186 insertions(+)
 create mode 100644 linked-list/circularLinkedList.js

diff --git a/linked-list/circularLinkedList.js b/linked-list/circularLinkedList.js
new file mode 100644
index 00000000..09a98e05
--- /dev/null
+++ b/linked-list/circularLinkedList.js
@@ -0,0 +1,186 @@
+function circularLinkedList() {
+    // creating a node for the linked list
+    let Node = function (nodeValue) {
+      	this.element = nodeValue;
+      	this.next = null;
+    }
+  
+    let length = 0;
+    let head = null;
+
+    // Get node at specific index
+    this.getNodeAt = function (index) {
+      	if (index >= 0 && index <= length) {
+        	let node = head;
+        	for (let i = 0; i < index && node != null; i++){
+          		node = node.next;
+        	}
+        	return node;
+      	}
+      	return undefined;
+    }
+    
+    // Add new node
+    this.append = function (element) {
+		// create new node
+		const node = new Node(element);
+		let current;
+		
+		// If head is empty, then make new node head
+		if (head === null) {
+			head = node;
+		} else {
+			// Else add the new node as the next node and mark the next of new node to the head
+			current = this.getNodeAt(length - 1);
+			current.next = node;
+		}
+		
+		node.next = head;
+		length++;
+    }
+    
+    // Insert at given position
+    this.insertAtPosition = function (element, index) {
+		if (index >= 0 && index <= length) {
+			const node = new Node (element);
+			let current = head;
+			
+			// Insert at head
+			if (index === 0) {      
+				if (head === null) {
+					head = node;
+					node.next = head;
+				} else {
+					node.next = current;
+					current = this.getNodeAt(length);
+					head = node;
+					current.next = head;
+				}
+			} else {
+				// Insert at given index (middle or end)
+				const previous = this.getNodeAt(index - 1);
+				node.next = previous.next;
+				previous.next = node;
+			}
+			
+			length++;
+			return true;
+		}
+		return false;
+    }
+    
+    // Remove at any position
+    this.removeAt = function (index) {
+		if (index >= 0 && index < length) {
+			let current = head;
+			
+			// Remove from head
+			if (index === 0) {
+				if (length === 1) {
+					head = undefined;
+				} else {
+					const removed = head;
+					current = this.getNodeAt(length - 1);
+					head = head.next;
+					current.next = head;
+					current = removed;
+				}
+			} else {
+				// Remove at given index (middle or end)
+				const previous = this.getNodeAt(index - 1);
+				current = previous.next;
+				previous.next = current.next;
+			}
+			
+			length--;
+			return current.element;
+		}
+		return undefined;
+    }
+    
+    // Get the indexOf item 
+    this.indexOf = function (elm) {
+		let current = head,
+		index = -1;
+	
+		// If element found then return its position
+		while (current) {
+			if (elm === current.element) {
+				return ++index;
+			}
+			index++;
+			current = current.next;
+		}
+	
+		// Else return -1
+		return -1;
+    };
+    
+    // Find the item in the list
+    this.isPresent = (elm) => {
+      	return this.indexOf(elm) !== -1;
+    };
+    
+    // Get the head
+    this.getHead = function() {
+      	return head;
+    }
+    
+    // Delete an item from the list
+    this.delete = (elm) => {
+    	return this.removeAt(this.indexOf(elm));
+    }; 
+    
+    // Delete the first item from the list
+    this.deleteHead = function() {
+      	this.removeAt(0);
+    }
+    
+    // Print item of the string
+    this.toString = function() {
+		let current = head,
+		string = '';
+		const temp = head.element;
+		
+		while (current) {
+			if (temp === current.next.element) {
+				string += current.element + (current.next ? '\n' : '');
+				break;
+			}
+			string += current.element + (current.next ? '\n' : '');
+			current = current.next;
+		}
+	
+		return string;
+    };
+    
+    // Convert list to array
+    this.toArray = function() {
+		let arr = [],
+		current = head;
+		const temp = head.element
+	
+		while (current) {
+			// Break if first element detected
+			if (temp === current.next.element) {
+				arr.push(current.element);
+				break;
+			}
+			arr.push(current.element);
+			current = current.next;
+		}
+	
+		return arr;
+    };
+    
+    // Check if list is empty
+    this.isEmpty = function() {
+      	return length === 0;
+    };
+    
+    // Get the size of the list
+    this.size = function() {
+      	return length;
+    }
+    
+  }
\ No newline at end of file