Add week 7 solutions : binaryTreeLevelOrderTraversal

Author: yolophg

binary-tree-level-order-traversal/yolophg.js

@@ -0,0 +1,33 @@
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+
+var levelOrder = function (root) {
+  // if the root is null, return an empty array.
+  if (root === null) return [];
+
+  const result = [];
+  const queue = [root];
+
+  // while there are nodes in the queue,
+  while (queue.length > 0) {
+    const levelSize = queue.length;
+    const currentLevel = [];
+
+    // loop nodes in the current level.
+    for (let i = 0; i < levelSize; i++) {
+      // dequeue the front node.
+      const currentNode = queue.shift();
+      // add value to the current level array.
+      currentLevel.push(currentNode.val);
+      // enqueue left child if exists.
+      if (currentNode.left) queue.push(currentNode.left);
+      // enqueue right child if exists.
+      if (currentNode.right) queue.push(currentNode.right);
+    }
+
+    // add the current level array to the result.
+    result.push(currentLevel);
+  }
+
+  return result;
+};