1
# Runtime: 77 ms (Top 11.09%) | Memory: 13.8 MB (Top 99.05%)
2
class Solution:
3
    def isValidSerialization(self, preorder: str) -> bool:
4
        nodes = preorder.split(",")
5
        counter = 1
6
        for i, node in enumerate(nodes):
7
            if node != "#":
8
                counter += 1
9
            else:
10
                if counter <= 1 and i != len(nodes) - 1:
11
                    return False
12
                counter -= 1
13
        return counter == 0