[LeetCode][python3]Day30. Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree (30-Day LeetCoding Challenge)

30 days! Lets go Lets go!
N2I -2020.04.30

1. My solution

class Solution:
    def isValidSequence(self, root: TreeNode, arr: List[int]) -> bool:
        if not root and arr:
            return False
        buffer1=[root]
        buffer2=[]
        f=lambda x:x.val if x else None
        for item in arr[:-1]:
            buffer2=[x for x in buffer1 if f(x)==item]
            if not buffer2:
                return False
            buffer1=[]
            for x in buffer2:
                buffer1.append(x.left)
                buffer1.append(x.right)
        for x in buffer1:
            if x and x.val==arr[-1]:
                if x.left==None and x.right==None:
                    return True
        return False

Explanation:

The Solution use two buffer. It checks elements in buffer1 if element.val==target. Then throw their child nodes back to buffer1.