# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def maxDepth(self, root: TreeNode) -> int:
# 遞歸求解樹(shù)的高度
if not root:
return 0
if not root.left and not root.right:
return 1
return max(self.maxDepth(root.left), self.maxDepth(root.right)) + 1
------------------------------------------------------------------------------------------------
# 迭代求解樹(shù)的高度
if not root:
return 0
treeHeight = 0
queue = [root]
while queue:
next_queue = []
treeHeight = treeHeight + 1
for node in queue:
if not node:
continue
if node.left:
next_queue.append(node.left)
if node.right:
next_queue.append(node.right)
queue = next_queue
return treeHeight
上面的第一種方法本質(zhì)上應(yīng)該是一種動(dòng)態(tài)規(guī)劃的解法徒探，第二種法中迭代法實(shí)際上的BFS的方式求解樹(shù)高，下面再給出第三種DFS求解樹(shù)高的方法：
class Solution:
def maxDepth(self, root: TreeNode) -> int:
self.levelHeight = 0
self.dfs(root, 1)
return self.levelHeight
def dfs(self, root, level):
if not root:
return 0
if self.levelHeight < level:
self.levelHeight += 1
self.dfs(root.left, level + 1)
self.dfs(root.right, level + 1)
