Add Two Numbers

Author: joshguha

.gitignore

@@ -1,4 +1,3 @@
-2-addTwoNumbers.js
 3-lengthOfLongestSubstring.js
 4-medianOfTwoSortedArrays.js
 5-longestPalindromicSubstring.js

2-addTwoNumbers.js

@@ -0,0 +1,81 @@
+// From LeetCode
+
+// You are 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.
+
+// You may assume the two numbers do not contain any leading zero, except the number 0 itself.
+
+// @param {ListNode} l1
+// @param {ListNode} l2
+// @return {ListNode}
+
+function ListNode(val, next) {
+    this.val = val === undefined ? 0 : val;
+    this.next = next === undefined ? null : next;
+}
+
+// Create Linked lists from numbers
+
+createLinkedListNumber = function (number) {
+    const remainder = number % 10;
+    const division = Math.floor(number / 10);
+    if (division !== 0) {
+        return new ListNode(remainder, createLinkedListNumber(division));
+    } else {
+        return new ListNode(remainder, undefined);
+    }
+};
+
+printLinkedListNumber = function (linkedListNumber) {
+    let num = linkedListNumber;
+    let nextNum = num.next;
+
+    while (true) {
+        console.log(num.val);
+
+        if (nextNum === null) {
+            break;
+        }
+        num = nextNum;
+        nextNum = num.next;
+    }
+};
+
+// Solution /////////////////////////
+var addTwoNumbers = function (l1, l2, carryover = 0) {
+    console.log(`Carryover is: ${carryover}`);
+    if (l1 === null && l2 === null) {
+        if (carryover === 1) {
+            return new ListNode(1, null);
+        }
+        return null;
+    } else if (l1 === null) {
+        if (l2.val + carryover >= 10) {
+            return new ListNode(
+                (l2.val + carryover) % 10,
+                addTwoNumbers(null, l2.next, 1)
+            );
+        }
+        return new ListNode(l2.val + carryover, addTwoNumbers(null, l2.next));
+    } else if (l2 === null) {
+        if (l1.val + carryover >= 10) {
+            return new ListNode(
+                (l1.val + carryover) % 10,
+                addTwoNumbers(l1.next, null, 1)
+            );
+        }
+        return new ListNode(l1.val + carryover, addTwoNumbers(l1.next, null));
+    } else {
+        const sum = l1.val + l2.val + carryover;
+        if (sum >= 10) {
+            return new ListNode(sum % 10, addTwoNumbers(l1.next, l2.next, 1));
+        }
+        return new ListNode(sum, addTwoNumbers(l1.next, l2.next));
+    }
+};
+
+const linkedListNumber1 = createLinkedListNumber(999);
+const linkedListNumber2 = createLinkedListNumber(1);
+
+printLinkedListNumber(addTwoNumbers(linkedListNumber1, linkedListNumber2));