leaf-similar-trees.py

# Time:  O(n)
# Space: O(h)

# 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.
#
# Note:
# - Both of the given trees will have between 1 and 100 nodes.

import itertools


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


class Solution(object):
    def leafSimilar(self, root1, root2):
        """
        :type root1: TreeNode
        :type root2: TreeNode
        :rtype: bool
        """
        def dfs(node):
            if not node:
                return
            if not node.left and not node.right:
                yield node.val
            for i in dfs(node.left):
                yield i
            for i in dfs(node.right):
                yield i
        return all(a == b for a, b in
                   itertools.izip_longest(dfs(root1), dfs(root2)))