diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md
index df1790c3..eca4acf4 100644
--- a/problems/0102.二叉树的层序遍历.md
+++ b/problems/0102.二叉树的层序遍历.md
@@ -421,9 +421,10 @@ var levelOrderBottom = function(root) {
             node.left&&queue.push(node.left);
             node.right&&queue.push(node.right);
         }
-        res.push(curLevel);
+	// 从数组前头插入值，避免最后反转数组，减少运算时间
+        res.unshift(curLevel);
     }
-    return res.reverse();
+    return res;
 };
 ```