Python树的序列化与反序列化的实现

class TreeNode:
    def __init__(self, value):
        self.val = value
        self.left = None
        self.right = None

def serialize(root):
    if not root:
        return "null"
    
    left = serialize(root.left)
    right = serialize(root.right)
    
    return str(root.val) + "," + left + "," + right

from collections import deque

def serialize_level_order(root):
    if not root:
        return "null"
    
    result = []
    queue = deque([root])
    
    while queue:
        node = queue.popleft()
        if node:
            result.append(str(node.val))
            queue.append(node.left)
            queue.append(node.right)
        else:
            result.append("null")
    
    return ",".join(result)

def deserialize(data):
    def helper(values):
        val = values.pop(0)
        if val == "null":
            return None
        node = TreeNode(int(val))
        node.left = helper(values)
        node.right = helper(values)
        return node

    values = data.split(",")
    return helper(values)

def deserialize_level_order(data):
    values = data.split(",")
    if not values or values[0] == "null":
        return None

    root = TreeNode(int(values[0]))
    queue = deque([root])
    i = 1

    while i < len(values):
        current = queue.popleft()

        left_val = values[i]
        i += 1
        if left_val != "null":
            current.left = TreeNode(int(left_val))
            queue.append(current.left)

        right_val = values[i]
        i += 1
        if right_val != "null":
            current.right = TreeNode(int(right_val))
            queue.append(current.right)

    return root

# 构建二叉树
"""
        1
       / \
      2   3
     / \
    4   5
"""
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 前序遍历序列化
serialized_tree = serialize(root)
print("前序遍历序列化:", serialized_tree)

# 前序遍历反序列化
deserialized_tree = deserialize(serialized_tree)

# 验证反序列化结果
def print_tree(root):
    if root:
        print_tree(root.left)
        print(root.val, end=" ")
        print_tree(root.right)

print("反序列化后的树:")
print_tree(deserialized_tree)

# 层序遍历序列化
serialized_tree_level_order = serialize_level_order(root)
print("层序遍历序列化:", serialized_tree_level_order)

# 层序遍历反序列化
deserialized_tree_level_order = deserialize_level_order(serialized_tree_level_order)

# 验证反序列化结果
print("反序列化后的树:")
print_tree(deserialized_tree_level_order)