g0301_0400.s0331_verify_preorder_serialization_of_a_binary_tree

Class Solution

java.lang.Object

g0301_0400.s0331_verify_preorder_serialization_of_a_binary_tree.Solution

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.

• For example, it could never contain two consecutive commas, such as "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 <= 104
• preorder consist of integers in the range [0, 100] and '#' separated by commas ','.

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
boolean	isValidSerialization(String preorder)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

isValidSerialization

public boolean isValidSerialization(String preorder)