1609. Even Odd Tree

https://leetcode.com/problems/even-odd-tree

Description

A binary tree is named Even-Odd if it meets the following conditions:

• The root of the binary tree is at level index 0, its children are at level index 1, their children are at level index 2, etc.

• For every even-indexed level, all nodes at the level have odd integer values in strictly increasing order (from left to right).

• For every odd-indexed level, all nodes at the level have even integer values in strictly decreasing order (from left to right).

Given the root of a binary tree, return true if the binary tree is Even-Odd, otherwise return false.

Example 1:

**Input:** root = [1,10,4,3,null,7,9,12,8,6,null,null,2]
**Output:** true
**Explanation:** The node values on each level are:
Level 0: [1]
Level 1: [10,4]
Level 2: [3,7,9]
Level 3: [12,8,6,2]
Since levels 0 and 2 are all odd and increasing, and levels 1 and 3 are all even and decreasing, the tree is Even-Odd.

Example 2:

**Input:** root = [5,4,2,3,3,7]
**Output:** false
**Explanation:** The node values on each level are:
Level 0: [5]
Level 1: [4,2]
Level 2: [3,3,7]
Node values in the level 2 must be in strictly increasing order, so the tree is not Even-Odd.

Example 3:

**Input:** root = [5,9,1,3,5,7]
**Output:** false
**Explanation:** Node values in the level 1 should be even integers.

Example 4:

**Input:** root = [1]
**Output:** true

Example 5:

**Input:** root = [11,8,6,1,3,9,11,30,20,18,16,12,10,4,2,17]
**Output:** true

Constraints:

• The number of nodes in the tree is in the range [1, 105].

• 1 <= Node.val <= 106

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