add new data structures (Single Circular Linked List) (#400)

* add new data structures (Single Circular Linked List)

* fix standard

* fix standard js

* fix code standard

Data-Structures/Linked-List/SingleCircularLinkedList.js.js

@@ -0,0 +1,97 @@
+class Node {
+  constructor (data, next = null) {
+    this.data = data
+    this.next = next
+  }
+}
+
+class SinglyCircularLinkedList {
+  constructor () {
+    this.head = null
+    this.size = 0
+  }
+
+  insert (data) {
+    const node = new Node(data)
+
+    if (!this.head) {
+      node.next = node
+      this.head = node
+      this.size++
+    } else {
+      node.next = this.head
+
+      let current = this.head
+
+      while (current.next.data !== this.head.data) {
+        current = current.next
+      }
+
+      current.next = node
+      this.size++
+    }
+  }
+
+  insertAt (index, data) {
+    const node = new Node(data)
+
+    if (index < 0 || index > this.size) return
+
+    if (index === 0) {
+      this.head = node
+      this.size = 1
+      return
+    }
+
+    let previous
+    let count = 0
+    let current = this.head
+
+    while (count < index) {
+      previous = current
+      current = current.next
+      count++
+    }
+
+    node.next = current
+    previous.next = node
+    this.size++
+  }
+
+  remove () {
+    if (!this.head) return
+
+    let prev
+    let current = this.head
+
+    while (current.next !== this.head) {
+      prev = current
+      current = current.next
+    }
+
+    prev.next = this.head
+    this.size--
+  }
+
+  printData () {
+    let count = 0
+    let current = this.head
+
+    while (current !== null && count !== this.size) {
+      console.log(current.data + '\n')
+      current = current.next
+      count++
+    }
+  }
+}
+
+const ll = new SinglyCircularLinkedList()
+
+ll.insert(10)
+ll.insert(20)
+ll.insert(30)
+ll.insert(40)
+ll.insert(50)
+ll.insertAt(5, 60)
+ll.remove(5)
+ll.printData()