Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree scould also be considered as a subtree of itself.
Example 1:
Given tree s:
3 / \ 4 5 / \ 1 2
Given tree t:
4 / \ 1 2
Return true, because t has the same structure and node values with a subtree of s.
Example 2:
Given tree s:
3 / \ 4 5 / \ 1 2 / 0
Given tree t:
4 / \ 1 2
Return false.
LeetCode:链接
给定两个非空二叉树s和t,判断t是否是s的子树。s的子树是指由s中某节点及该节点的所有子节点构成的二叉树。
特别的,s是其本身的子树。
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def isSubtree(self, s, t):
"""
:type s: TreeNode
:type t: TreeNode
:rtype: bool
"""
# 必须都为空才行
if not s or not t:
return not s and not t
if self.check(s, t):
return True
return self.isSubtree(s.left, t) or self.isSubtree(s.right, t)
def check(self, s, t):
if not s or not t:
return not s and not t
if s.val != t.val:
return False
# 必须左子树右子树都得满足
return self.check(s.left, t.left) and self.check(s.right, t.right)