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Serialize and Deserialize BST in Python
Suppose we want to design an algorithm to serialize and deserialize a binary search tree. Serialization is the process of converting something (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. This can be reconstructed later that process is deserialization.
So, if the input is like [5,2,9,1,3,7], then the output will be Serialized output 5.2.9.1.3.7.N.N.N.N.N.N.N Deserialized output: 1, 2, 3, 5, 7, 9, (inorder traversal)
To solve this, we will follow these steps −
Define a function serialize() . This will take root
res := a new list
define one queue and insert root
while queue is non-empty, do
while queue is not empty, do
current := queue[0]
insert current at the end of res
delete first element from queue
if current is non-zero, then
come out from the loop
if current is null, then
come out from the loop
if current.left is not null, then
insert current.left at the end of queue
otherwise,
insert None at the end of queue
if current.right is not null, then
insert current.right at the end of queue
otherwise,
insert None at the end of queue
s:= blank string
for i in range 0 to size of res, do
if res[i] is non-zero, then
s := s concatenate res[i].data
otherwise,
s := s concatenate "N"
if i is same as size of res -1, then
come out from the loop
s := s concatenate "."
return s
Define a function deserialize() . This will take data
data := a list of parts after dividing the data using dot
stack := a new list
if data[0] is same as 'N', then
return None
root := create a new node with data data[0]
insert root at the end of stack
i := 1
current := 0
while i < size of data, do
left:= False
if data[i] is not same as 'N', then
temp := create a new node with data data[i]
stack[current].left := temp
insert temp at the end of stack
otherwise,
stack[current].left := None
i := i + 1
if data[i] is not same as 'N', then
temp := create a new node with data data[i]
stack[current].right := temp
insert temp at the end of stack
otherwise,
stack[current].right := None
current := current + 1
i := i + 1
return root
Example
Let us see the following implementation to get a better understanding −
class TreeNode:
def __init__(self, data, left = None, right = None):
self.data = data
self.left = left
self.right = right
def insert(temp,data):
que = []
que.append(temp)
while (len(que)):
temp = que[0]
que.pop(0)
if (not temp.left):
if data is not None:
temp.left = TreeNode(data)
else:
temp.left = TreeNode(0)
break
else:
que.append(temp.left)
if (not temp.right):
if data is not None:
temp.right = TreeNode(data)
else:
temp.right = TreeNode(0)
break
else:
que.append(temp.right)
def make_tree(elements):
Tree = TreeNode(elements[0])
for element in elements[1:]:
insert(Tree, element)
return Tree
def print_tree(root):
#print using inorder traversal
if root is not None:
print_tree(root.left)
print(root.data, end = ', ')
print_tree(root.right)
class Codec:
def serialize(self, root):
res =[]
queue = [root]
while queue:
while True and queue:
current = queue[0]
res.append(current)
queue.pop(0)
if current:
break
if not current:
break
if current.left:
queue.append(current.left)
else:
queue.append(None)
if current.right:
queue.append(current.right)
else:
queue.append(None)
s=""
for i in range(len(res)):
if res[i]:
s+=str(res[i].data)
else:
s+="N"
if i == len(res)-1:
break
s+="."
return s
def deserialize(self, data):
data = data.split(".")
stack = []
if data[0]=='N':
return None
root = TreeNode(int(data[0]))
stack.append(root)
i = 1
current = 0
while i <len(data):
left= False
if data[i] !='N':
temp = TreeNode(int(data[i]))
stack[current].left = temp
stack.append(temp)
else:
stack[current].left = None
i+=1
if data[i] !='N':
temp = TreeNode(int(data[i]))
stack[current].right = temp
stack.append(temp)
else:
stack[current].right = None
current+=1
i+=1
return root
ob = Codec()
root = make_tree([5,2,9,1,3,7])
ser = ob.serialize(root)
print('Serialization:',ser)
print_tree(ob.deserialize(ser))Input
[5,2,9,1,3,7]
Output
Serialization: 5.2.9.1.3.7.N.N.N.N.N.N.N 1, 2, 3, 5, 7, 9,
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