Medium
Quiz
#331 Verify Preorder Serialization of a Binary Tree
APPROACH
One way to serialize a binary tree uses preorder traversal, recording node values and using a sentinel value such as '#' for null nodes.
Given a comma-separated string preorder, return true if it is a valid preorder serialization of some binary tree, or false otherwise.
Each token is either an integer or '#'. 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
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What is the optimal approach for this problem?