331. 验证二叉树的前序序列化
public class Solution {
public bool IsValidSerialization(string preorder) {
var arr = preorder.Split(',');
if (arr.Length == 0)
return true;
if (arr.Length % 2 == 0)
return false;
var degree = 1;
foreach (var ch in arr) {
if (degree == 0)
return false;
degree += (ch == "#" ? -1 : +1);
}
return degree == 0;
}
}