Verify Preorder Serialization of a Binary Tree

reference:
https://leetcode.com/discuss/83824/7-lines-easy-java-solution
https://leetcode.com/discuss/105664/clear-c-solution

c++

class Solution {public:    bool isValidSerialization(string preorder) {        int degree = 1;        string x;        stringstream ss(preorder);        while (getline(ss, x, ',')) {            degree--;            if (degree < 0) return false;            if (x != "#") degree += 2;        }        return degree == 0;    }};

python

class Solution(object):    def isValidSerialization(self, preorder):        """        :type preorder: str        :rtype: bool        """        s = preorder.split(',')        degree = 1        for x in s:            degree -= 1 # in degree             if degree<0:return False            if x != '#': degree += 2 # out degree         return degree == 0