[Leetcode] [JavaScript] Verify preorder serialization of a Binary Tree

Verify preorder serialization of a Binary Tree

One-to-serialize a binary tree is-to-use pre-order 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 # .

     _9_    /      3     2  /\   /  4   1  #  6/\/\   /#   # # # # # # # # #

For example, the above binary tree can "9,3,4,#,#,1,#,#,2,#,6,#,#" is serialized to the string, where # represents a null node.

Given a string of comma separated values, verify whether it is a correct preorder traversal serialization of a binary tree . Find an algorithm without reconstructing the tree.

Each comma separated value in the string must is either an integer or a character ‘#‘ representing null pointer.

Assume that the input format is always valid, for example it could never contain, consecutive commas such as .

Example 1:
"9,3,4,#,#,1,#,#,2,#,6,#,#"
Returntrue

Example 2:
"1,#"
Returnfalse

Example 3:
"9,#,#,1"
Returnfalse

https://leetcode.com/problems/verify-preorder-serialization-of-a-binary-tree/

To determine whether the given sequence is a number ordinal traversal sequence.

The idea is to "dig holes", if the first is a number, that is the root node, it can be placed around 2 nodes, there are two "holes."

If it is ' # ', fill in a hole, and if it is a number, fill in a hole and add two holes.

When the hole is not enough or the final hole is not filled, it means that it is not sequential traversal sequence.

1 /**2 * @param {string} preorder3 * @return {Boolean}4  */5 varIsvalidserialization =function(preorder) {6     varspilted = Preorder.split (', '), holes = 0;7     if(Spilted.length = = 0)return true;8     if(Spilted[0]!== ' # ') holes + = 2;9      for(vari = 1; i < spilted.length; i++){Ten         if(Spilted[i]!== ' # '){ One             if(Holes > 0) holes++; A             Else return false; -}Else{ -holes--; the         } -         if(Holes < 0)return false; -     } -     returnHoles = = = 0?true:false; +};

[Leetcode] [JavaScript] Verify preorder serialization of a Binary Tree