LeetCode 297. Serialize and Deserialize Binary Tree

파이썬 알고리즘 인터뷰 문제 47번(리트코드 297번) Serialize and Deserialize Binary Tree
https://leetcode.com/problems/serialize-and-deserialize-binary-tree/

나의 풀이(DFS, Recursive)

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Codec:

    def serialize(self, root):
        """Encodes a tree to a single string.
        
        :type root: TreeNode
        :rtype: str
        """
        result = []
        
        def helper(root):
            if not root:
                result.append('null')
                return
            result.append(str(root.val))
            helper(root.left)
            helper(root.right)
            
        helper(root)
        return ",".join(result)

    def deserialize(self, data):
        """Decodes your encoded data to tree.
        
        :type data: str
        :rtype: TreeNode
        """
        
        result = collections.deque(data.split(','))

        def helper(val):
            if val == 'null':
                return None
            node = TreeNode(int(val))
            node.left = helper(result.popleft())
            node.right = helper(result.popleft())
            return node

        return helper(result.popleft())
        
# Your Codec object will be instantiated and called as such:
# ser = Codec()
# deser = Codec()
# ans = deser.deserialize(ser.serialize(root))

다른 풀이(BFS, Queue)

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Codec:

    def serialize(self, root):
        """Encodes a tree to a single string.
        
        :type root: TreeNode
        :rtype: str
        """
        queue = collections.deque([root])
        result = ['#']

        while queue:
            node = queue.popleft()
            if node:
                queue.append(node.left)
                queue.append(node.right)
                result.append(str(node.val))
            else:
                result.append('#')
        
        return " ".join(result)

    def deserialize(self, data):
        """Decodes your encoded data to tree.
        
        :type data: str
        :rtype: TreeNode
        """
        
        if data == '# #':
            return None
        
        nodes = data.split()
        root = TreeNode(int(nodes[1]))
        queue = collections.deque([root])
        index = 2

        while queue:
            node = queue.popleft()
            if nodes[index] is not '#':
                node.left = TreeNode(int(nodes[index]))
                queue.append(node.left)
            index += 1
            if nodes[index] is not '#':
                node.right = TreeNode(int(nodes[index]))
                queue.append(node.right)
            index += 1
        
        return root
        
# Your Codec object will be instantiated and called as such:
# ser = Codec()
# deser = Codec()
# ans = deser.deserialize(ser.serialize(root))