判断一棵树是不是另一棵树的子树

题目

判断b是不是a的子树

思路

先判断根节点是否一样，若一样则递归判断左右子树，若不一样就用b的根节点去比较a的左右子树。

代码

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def HasSubtree(self, pRoot1, pRoot2):
        result = False
        if  pRoot2 is None or pRoot1 is None:
            return False
        if pRoot1.val == pRoot2.val:
            result =  self.issubtree(pRoot1,pRoot2)
        if result is False:
            return self.HasSubtree(pRoot1.left,pRoot2) or self.HasSubtree(pRoot1.right,pRoot2)
        return result
    def issubtree(self,node1,node2):
        if node2 is None:
            return True
        if node1 is None:
            return False
        if node1.val != node2.val:
            return False
        else:
            return self.issubtree(node1.left, node2.left) and self.issubtree(node1.right, node2.right)