# Given a binary tree where each path going from the root to any leaf form a valid sequence, check if a given string is a valid sequence in such binary tree. 

# We get the given string from the concatenation of an array of integers arr and the concatenation of all values of the nodes along a path results in a sequence in the given binary tree.

 

# Example 1:



# Input: root = [0,1,0,0,1,0,null,null,1,0,0], arr = [0,1,0,1]
# Output: true
# Explanation: 
# The path 0 -> 1 -> 0 -> 1 is a valid sequence (green color in the figure). 
# Other valid sequences are: 
# 0 -> 1 -> 1 -> 0 
# 0 -> 0 -> 0
# Example 2:



# Input: root = [0,1,0,0,1,0,null,null,1,0,0], arr = [0,0,1]
# Output: false 
# Explanation: The path 0 -> 0 -> 1 does not exist, therefore it is not even a sequence.
# Example 3:



# Input: root = [0,1,0,0,1,0,null,null,1,0,0], arr = [0,1,1]
# Output: false
# Explanation: The path 0 -> 1 -> 1 is a sequence, but it is not a valid sequence.
 

# Constraints:

# 1 <= arr.length <= 5000
# 0 <= arr[i] <= 9
# Each node's value is between [0 - 9].

# 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 isValidSequence(self, root: TreeNode, arr: List[int]) -> bool:
        return self.check(root, arr, len(arr), 0)
    
    def check(self, root, arr, length, index):
        if root is None:
            return length == 0
        if (root.left == None and root.right == None) and index == length - 1 and root.val == arr[index]:
            return True
        return (index < length and root.val == arr[index] and (self.check(root.left, arr, length, index + 1) or self.check(root.right, arr, length, index + 1)))    