331. Verify Preorder Serialization of a Binary Tree
Medium
30 Points
String
Stack
Tree
Binary Tree
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.
Note: You are not allowed to reconstruct the tree.
Examples
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 ','.
331. Verify Preorder Serialization of a Binary Tree
Medium
30 Points
String
Stack
Tree
Binary Tree
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.
Note: You are not allowed to reconstruct the tree.
Examples
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 ','.