Leetcode 1731 Solution

This article provides solution to leetcode question 1731 (even-odd-tree)
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https://leetcode.com/problems/even-odd-tree

Solution

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def isEvenOddTree(self, root: Optional[TreeNode]) -> bool:
        level = 0
        q = collections.deque()
        q.append(root)



        while q:
            s = len(q)



            if level % 2 == 0:
                last_val = 0
            else:
                last_val = sys.maxsize



            for _ in range(s):
                child_node = q.popleft()



                if level % 2 == child_node.val % 2:
                    return False



                if level % 2 == 0:
                    if child_node.val <= last_val:
                        return False
                else:
                    if child_node.val >= last_val:
                        return False



                last_val = child_node.val



                if child_node.left:
                    q.append(child_node.left)
                if child_node.right:
                    q.append(child_node.right)



            level += 1



        return True