这篇文章主要介绍了python中遍历树的方法有哪些,具有一定借鉴价值,需要的朋友可以参考下。希望大家阅读完这篇文章后大有收获。下面让小编带着大家一起了解一下。
各种遍历顺序如下图所示:
树的最大深度
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def maxdepth(self, root):
if root is None:
return 0
return max(self.maxdepth(root.left), self.maxdepth(root.right))+1
深度优先
深度优先遍历有三种方式:前序遍历、中序遍历和后序遍历
所说的前序、中序、后序,是指根节点的先后顺序。
前序遍历:根节点 -> 左子树 -> 右子树
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def preorder(self, root):
if root is None:
return ''
print root.val
if root.lef:
self.preorder(root.left)
if root.right:
self.preorder(root.right)
中序遍历:左子树 -> 根节点 -> 右子树
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def midorder(self, root):
if root is None:
return ''
if root.lef:
self.midorder(root.left)
print root.val
if root.right:
self.midorder(root.right)
后序遍历:左子树 -> 右子树 -> 根节点
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def endorder(self, root):
if root is None:
return ''
if root.lef:
self.endorder(root.left)
if root.right:
self.endorder(root.right)
print root.val
广度优先
广度优先遍历,即层次遍历,优先遍历兄弟节点
层次遍历:根节点 -> 左节点 -> 右节点
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def graorder(self, root):
if root is None:
return ''
queue = [root]
while queue:
res = []
for item in queue:
print item.val,
if item.left:
res.append(item.left)
if item.right:
res.apppend(item.right)
queue = res
比较两棵树是否相同
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def issame(self, root1, root2):
if root1 is None and root2 is None:
return True
elif root1 and root2:
return root1.val==root2.val and issame(root1.left, root2.left) and issame(root1.right, root2.right)
else:
return False
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