[Leetcode] 100. Same Tree

題目 : 100. Same Tree

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

Example 1:

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

Example 2:

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

Example 3:

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

1.

# 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: Optional[TreeNode], q: Optional[TreeNode]) -> bool:
        # 如果p和q的node都是None，代表比對完成
        if p == None and q == None:
            return True
        # 如果p和q的node如果有一個是None，代表其中一個已經沒有node可以比對
        # p和q不相等，回傳False
        if p== None or q == None:
            return False
 
        #        比對p和q的node值                     比對左子樹                             比對右子樹
        # 如果3個都是True，代表p和q是相同的tree
        return (p.val == q.val) and self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)