# Test case wrong

• Input:
[1,2,2,3,3,3,3,4,4,4,4,4,4,null,null,5,5]
Output:
false
Expected:
true

This test case is a tree like the following:

``````          1
2       2
3   3   3   3
4 4 4 4 4 4
5 5
``````

It is not balanced, right?

• It's balanced. the depth of a tree is the same as the max depth of the tree.

• It's balanced. The depth of the left node of the node 1 is 4, and the depth of the right node of the node is 3. 4 and 3 are not differed by more than 1 so it's balanced.

• leftmost node of node 1 appears to be on level 5 while rightmost node on level 3. I'm also puzzled with this test case

• Ok, got it. It is more clear from more explicit definition. Heights of left and right subtress are in did not different by more then 1 inspite min depth and max depth are different by 2:
An empty tree is height-balanced. A non-empty binary tree T is balanced if:

1. Left subtree of T is balanced
2. Right subtree of T is balanced
3. The difference between heights of left subtree and right subtree is not more than 1.

• 1st level: left depth=4, right depth=3

2nd level: left.left depth=3, right.right depth=2. right.left depth=2, right.right=1

... and so on.

Each parent is balanced and both children of each parent are balanced, then the tree is balanced.

I guess your codes is level-order travel, so you get this result.

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