Package g0301_0400.s0331_verify_preorder_serialization_of_a_binary_tree

Class 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 Detail

      • Solution

        public Solution()

    • Method Detail

      • isValidSerialization

        public boolean isValidSerialization​(String preorder)