Add binary-tree-level-order-traversal solution

Author: Jeehay28

binary-tree-level-order-traversal/Jeehay28.js

@@ -0,0 +1,37 @@
+// ✅ Time Complexity: O(n), where n is the number of nodes in the tree
+// ✅ Space Complexity: O(n)
+
+/**
+ * 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) {
+  if (!root) return [];
+
+  let output = [];
+  let queue = [root];
+
+  while (queue.length > 0) {
+    let values = [];
+
+    const lengthQueue = queue.length;
+
+    for (let i = 0; i < lengthQueue; i++) {
+      const node = queue.shift();
+      values.push(node.val);
+      if (node.left) queue.push(node.left);
+      if (node.right) queue.push(node.right);
+    }
+    output.push(values);
+  }
+  return output;
+};
+