merge: Implement Add Two Numbers (Linked List) (#888)

* Implement Add Two Numbers (Linked List)

* Implement Add Two Numbers (Linked List)

* Implement Add Two Numbers (Linked List)

Co-authored-by: Shakil Ahmmed <shakilahmmed@ShakilAhmmeds-MacBook-Pro.local>

Data-Structures/Linked-List/AddTwoNumbers.js

@@ -0,0 +1,59 @@
+/**
+ * A LinkedList based solution for Add Two Numbers
+ *
+ */
+import { Node } from './SinglyLinkedList.js'
+
+/*
+Problem Statement:
+Given two non-empty linked lists representing two non-negative integers.
+The digits are stored in reverse order and each of their nodes contain a single digit.
+Add the two numbers and return it as a linked list.
+
+Link for the Problem: https://leetcode.com/problems/add-two-numbers/
+*/
+
+class AddTwoNumbers {
+  constructor () {
+    this.dummyNode = new Node(0)
+  }
+
+  solution (firstList, secondList) {
+    let firstRunner = firstList
+    let secondRunner = secondList
+    let tail = this.dummyNode
+    let carry = 0
+    while (firstRunner != null || secondRunner != null) {
+      const firstNumber = firstRunner ? firstRunner.data : 0
+      const secondNumber = secondRunner ? secondRunner.data : 0
+      const sum = carry + firstNumber + secondNumber
+      carry = parseInt(sum / 10)
+      tail.next = new Node(sum % 10)
+      tail = tail.next
+      if (firstRunner) {
+        firstRunner = firstRunner.next
+      }
+      if (secondRunner) {
+        secondRunner = secondRunner.next
+      }
+    }
+    if (carry > 0) {
+      tail.next = new Node(carry % 10)
+    }
+
+    return this.dummyNode.next
+  }
+
+  solutionToArray () {
+    const list = []
+    let currentNode = this.dummyNode.next
+    while (currentNode) {
+      list.push(currentNode.data)
+      currentNode = currentNode.next
+    }
+
+    return list
+  }
+}
+
+export { AddTwoNumbers }