Add solution #445

Author: JoshCrozier

README.md

@@ -353,6 +353,7 @@
 441|[Arranging Coins](./0441-arranging-coins.js)|Easy|
 442|[Find All Duplicates in an Array](./0442-find-all-duplicates-in-an-array.js)|Medium|
 443|[String Compression](./0443-string-compression.js)|Medium|
+445|[Add Two Numbers II](./0445-add-two-numbers-ii.js)|Medium|
 448|[Find All Numbers Disappeared in an Array](./0448-find-all-numbers-disappeared-in-an-array.js)|Easy|
 450|[Delete Node in a BST](./0450-delete-node-in-a-bst.js)|Medium|
 451|[Sort Characters By Frequency](./0451-sort-characters-by-frequency.js)|Medium|

solutions/0445-add-two-numbers-ii.js

@@ -0,0 +1,48 @@
+/**
+ * 445. Add Two Numbers II
+ * https://leetcode.com/problems/add-two-numbers-ii/
+ * Difficulty: Medium
+ *
+ * You are given two non-empty linked lists representing two non-negative integers. The most
+ * significant digit comes first and each of their nodes contains a single digit. Add the two
+ * numbers and return the sum as a linked list.
+ *
+ * You may assume the two numbers do not contain any leading zero, except the number 0 itself.
+ */
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} l1
+ * @param {ListNode} l2
+ * @return {ListNode}
+ */
+var addTwoNumbers = function(l1, l2) {
+  const s1 = [];
+  const s2 = [];
+  let carry = 0;
+  let head = null;
+
+  while (l1) {
+    s1.push(l1.val);
+    l1 = l1.next;
+  }
+
+  while (l2) {
+    s2.push(l2.val);
+    l2 = l2.next;
+  }
+
+  while (s1.length || s2.length || carry) {
+    const sum = (s1.pop() || 0) + (s2.pop() || 0) + carry;
+    carry = sum / 10 | 0;
+    head = Object.assign(new ListNode(sum % 10), { next: head });
+  }
+
+  return head;
+};