100. Same Tree

Given the roots of two binary trees p and q, 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:

1 2	Input: p = [1,2,3], q = [1,2,3] Output: true

Example 2:

1 2	Input: p = [1,2], q = [1,null,2] Output: false

Example 3:

1 2	Input: p = [1,2,1], q = [1,1,2] Output: false

判斷2棵樹一不一樣，就遍歷時看節點一不一樣。

T: O(N), S: O(log(N))
# Definition for a binary tree node.
# class TreeNode:
#     def init(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """    
        # p and q are both None
        if not p and not q:
            return True
        # one of p and q is None
        if not q or not p:
            return False
        if p.val != q.val: # root equal
            return False
        return self.isSameTree(p.right, q.right) and self.isSameTree(p.left, q.left) # leaf equal

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