LeetCode 872 Solution

Problem

Consider all the leaves of a binary tree, from left to right order, the values of those leaves form a leaf value sequence.

For example, in the given tree above, the leaf value sequence is (6, 7, 4, 9, 8).

Two binary trees are considered leaf-similar if their leaf value sequence is the same.

Return true if and only if the two given trees with head nodes root1 and root2 are leaf-similar.

Example 1:

• Input: root1 = [3,5,1,6,2,9,8,null,null,7,4], root2 = [3,5,1,6,7,4,2,null,null,null,null,null,null,9,8]
• Output: true

Constraints:

• The number of nodes in each tree will be in the range [1, 200].
• Both of the given trees will have values in the range [0, 200].

python

from typing import Optional

# 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 leafSimilar(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
        root1_leaf, root2_leaf = [], []
        self.leaf_list(root1, root1_leaf)
        self.leaf_list(root2, root2_leaf)
        return root1_leaf == root2_leaf

    def leaf_list(self, root, root_leaf):
        if root is None:
            return

        if root.left is None and root.right is None:
            root_leaf.append(root.val)
            return

        if root.left:
            self.leaf_list(root.left, root_leaf)

        if root.right:
            self.leaf_list(root.right, root_leaf)