Add solution #102

Author: JoshCrozier

README.md

@@ -41,6 +41,7 @@
 83|[Remove Duplicates from Sorted List](./0083-remove-duplicates-from-sorted-list.js)|Easy|
 88|[Merge Sorted Array](./0088-merge-sorted-array.js)|Easy|
 94|[Binary Tree Inorder Traversal](./0094-binary-tree-inorder-traversal.js)|Easy|
+102|[Binary Tree Level Order Traversal](./0102-binary-tree-level-order-traversal.js)|Medium|
 118|[Pascal's Triangle](./0118-pascals-triangle.js)|Easy|
 119|[Pascal's Triangle II](./0119-pascals-triangle-ii.js)|Easy|
 121|[Best Time to Buy and Sell Stock](./0121-best-time-to-buy-and-sell-stock.js)|Easy|

solutions/0102-binary-tree-level-order-traversal.js

@@ -0,0 +1,40 @@
+/**
+ * 102. Binary Tree Level Order Traversal
+ * https://leetcode.com/problems/binary-tree-level-order-traversal/
+ * Difficulty: Medium
+ *
+ * Given the root of a binary tree, return the level order traversal of its
+ * nodes' values. (i.e., from left to right, level by level).
+ */
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number[][]}
+ */
+var levelOrder = function(root) {
+  const result = [];
+
+  traverse(result, root);
+
+  return result;
+};
+
+function traverse(result, node, level = 0) {
+  if (!node) {
+    return [];
+  }
+
+  result[level] = result[level] || [];
+  result[level].push(node.val);
+
+  traverse(result, node.left, level + 1);
+  traverse(result, node.right, level + 1);
+}