[LeetCode] 100. Same Tree_Easy tag: DFS

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

思路基本的DFS, 都空, 为True, 都不为空, 判断value一样, 并且recursive children, 否则False

1. Constraints
1) 可以都为None => True

2. Ideas

DFS      O(n)

3. Code

class Solution:
    def sameTree(self, p, q):
        if not p and not q:
            return True
        if p and q and p.val == q.val:
            return self.sameTree(p.left, q.left) and self.sameTree(p.right, q.right)
        return False