leetcode100-python 相同的树

Given two binary trees, write a function to check if they are the same or not.

Two binary trees are considered the same if they are structurally identical and the nodes have the same value.

Example 1:

Input:     1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3]

Output: true

Example 2:

Input:     1         1
          /           \
         2             2

        [1,2],     [1,null,2]

Output: false

Example 3:

Input:     1         1
          / \       / \
         2   1     1   2

        [1,2,1],   [1,1,2]

Output: false

解题要点:

1.本来想着写个广度遍历放在list里面

class Solution:
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """
        pp = self.levelTree(p)
        qq = self.levelTree(q)
        if pp == qq:
            return True
        else:
            return False


    def levelTree(self, root):
        if root == None:
            return ["null"]
        que = []
        num = []
        node = root
        que.append(node)
        num.append(node.val)
        while que:
            node = que.pop(0)
            if node.left == None:
                num.append("null")
            else:
                que.append(node.left)
                num.append(node.left.val)
            if node.right == None:
                num.append("null")
            else:
                que.append(node.right)
                num.append(node.right.val)
        return num

2.后来看到别人写的,只需要判断每个节点十分相同就行了,比较效率;

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """
        if p == None and q == None:
            return True
        elif p == None or q == None: 
            return False
        else:
            if p.val == q.val:
                return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)
            else:
                return False


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