Package g1601_1700.s1609_even_odd_tree

Class Solution

  • public class Solution
extends Object
    1609 - Even Odd Tree\. Medium 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:** ![](https://assets.leetcode.com/uploads/2020/09/15/sample_1_1966.png) **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:** ![](https://assets.leetcode.com/uploads/2020/09/15/sample_2_1966.png) **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 level 2 must be in strictly increasing order, so the tree is not Even-Odd. **Example 3:** ![](https://assets.leetcode.com/uploads/2020/09/22/sample_1_333_1966.png) **Input:** root = [5,9,1,3,5,7] **Output:** false **Explanation:** Node values in the level 1 should be even integers. **Constraints:** * The number of nodes in the tree is in the range [1, 105]. * 1 <= Node.val <= 106

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • isEvenOddTree

        public boolean isEvenOddTree​(TreeNode root)