Package 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 java.lang.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
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    isValidSerialization(java.lang.String preorder)
     

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • isValidSerialization

      public boolean isValidSerialization(java.lang.String preorder)