leetcode-449 - Serialize and Deserialize BST

動機

因為是BST情況就沒有那麼複雜

Problem

Serialization is converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary search tree. There is no restriction on how your serialization/deserialization algorithm should work. You need to ensure that a binary search tree can be serialized to a string, and this string can be deserialized to the original tree structure.

The encoded string should be as compact as possible.

Example 1:

Input: root = [2,1,3]Output: [2,1,3]

Example 2:

Input: root = []Output: []

Constraints:

• The number of nodes in the tree is in the range [0, 104].
• 0 <= Node.val <= 104
• The input tree is guaranteed to be a binary search tree.

sol

class Codec:

    def serialize(self, r: Optional[TreeNode]) -> str:
        if not r:
            return ''
        else:
            return f'{r.val} {self.serialize(r.left)} {self.serialize(r.right)}'
        

    def deserialize(self, data: str) -> Optional[TreeNode]:
        preorder = [int(x) for x in data.split(" ") if x]
        inorder = list(sorted(preorder))
        def build(preo, ino):
            if not ino or not preo:
                return None
            else:
                ret = TreeNode(preo[0])
                i = ino.index(preo[0])
                ret.left = build(preo[1:1+i], ino[:i])
                ret.right = build(preo[1+i:], ino[i+1:])
                return ret
        return build(preorder,inorder)