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binary_tree_serializer.py
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binary_tree_serializer.py
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import collections
class TreeNode:
"""
Nodes are defined for the binary tree.
"""
def __init__(self, x):
self.val = x
self.left = self.right = None
class BinaryTreeSerializer:
"""
Converts a binary tree to a string, then reconstructs the original binary tree using that string.
This is done in O(n) time because it requires a single traversal across all nodes for either representation.
Example of tree: [1,2,3,null,null,4,5]
1 is root and has children: 2, 3
2 has no children: null, null
3 has children: 4, 5
Example of string: "1,2,3,x,x,4,5,x,x,x,x"
"""
def serialize(self, root):
"""
Encodes a tree to a single string using iterative level traversal.
"""
data = ""
queue = collections.deque([root])
while queue:
node = queue.popleft()
if node:
data += str(node.val) + ","
queue.append(node.left)
queue.append(node.right)
else:
data += "x" + ","
return data[:-1]
def deserialize(self, data):
"""
Decodes encoded data to tree using iterative level traversal.
"""
if not data or data == "x":
return []
data = data.split(",")
root = TreeNode(int(data[0]))
queue = collections.deque([root])
data = data[1:]
while data:
node = queue.popleft()
if data[0] != "x":
node.left = TreeNode(int(data[0]))
queue.append(node.left)
if data[1] != "x":
node.right = TreeNode(int(data[1]))
queue.append(node.right)
data = data[2:]
return root