public class Solution extends Object
331 - Verify Preorder Serialization of a Binary Tree.
Medium
One way to serialize a binary tree is to use preorder traversal. When we encounter a non-null node, we record the node’s value. If it is a null node, we record using a sentinel value such as '#'.

For example, the above binary tree can be serialized to the string "9,3,4,#,#,1,#,#,2,#,6,#,#", where '#' represents a null node.
Given a string of comma-separated values preorder, return true if it is a correct preorder traversal serialization of a binary tree.
It is guaranteed that each comma-separated value in the string must be either an integer or a character '#' representing null pointer.
You may assume that the input format is always valid.
"1,,3".**Note: **You are not allowed to reconstruct the tree.
Example 1:
Input: preorder = “9,3,4,#,#,1,#,#,2,#,6,#,#”
Output: true
Example 2:
Input: preorder = “1,#”
Output: false
Example 3:
Input: preorder = “9,#,#,1”
Output: false
Constraints:
1 <= preorder.length <= 104preorder consist of integers in the range [0, 100] and '#' separated by commas ','.| Constructor and Description |
|---|
Solution() |
public boolean isValidSerialization(String preorder)
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