[leetcode] 297. Serialize and Deserialize Binary Tree

 

Serialization is the process of 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 tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

Clarification: The input/output format is the same as how LeetCode serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

 

Example 1:

Input: root = [1,2,3,null,null,4,5]
Output: [1,2,3,null,null,4,5]

Example 2:

Input: root = []
Output: []

 

Constraints:

• The number of nodes in the tree is in the range [0, 104].
• -1000 <= Node.val <= 1000

 

# 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 = ['#']
        # 트리 BFS 직렬화 
        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))