题目
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.
解题思路
按层进行bfs，把每层的值存在一个数组里进行判断，是否全为奇/偶数，递增/递减
代码
# 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:
def is_increase(q, is_even):
if is_even:
if q[0].val % 2 == 0:
return False
for i in range(1, len(q)):
if q[i].val % 2 == 0:
return False
if q[i].val <= q[i - 1].val:
return False
else:
if q[0].val % 2 != 0:
return False
for i in range(1, len(q)):
if q[i].val % 2 != 0:
return False
if q[i].val >= q[i - 1].val:
return False
return True
is_even = True
q = [root]
while q:
if not is_increase(q, is_even):
return False
tmp = []
for n in q:
if n.left:
tmp.append(n.left)
if n.right:
tmp.append(n.right)
q = tmp[:]
is_even = not is_even
return True
