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feat: Implemented Morris postorder traversal for Binary tree

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kuntal0901 2024-10-05 19:22:01 +05:30
parent f08e77f6aa
commit 31bc93f1a2
1 changed files with 39 additions and 37 deletions
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76
data_structures/binary_tree/morris_inorder_traversal.py → data_structures/binary_tree/morris_postorder_traversal.py
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@ -1,8 +1,8 @@
""" """
Problem Statement: Given a binary perform an inorder traversal using Morris Inorder Problem Statement: Given a binary perform an postorder traversal using Morris Postorder
traversal algorithm. (Iterative version of Inorder traversal of tree) traversal algorithm. (Iterative version of Postorder traversal of tree)
https://www.geeksforgeeks.org/inorder-tree-traversal-without-recursion-and-without-stack/ https://www.geeksforgeeks.org/morris-traversal-for-postorder/
""" """
@ -35,8 +35,8 @@ class BinaryTree:
insert(value: int) -> None: insert(value: int) -> None:
Insert a value into the binary tree following binary search tree (BST) rules. Insert a value into the binary tree following binary search tree (BST) rules.
morris_inorder_traversal() -> List[int]: morris_postorder_traversal() -> List[int]:
Perform inorder traversal and return list of node values. Perform postorder traversal and return list of node values.
>>> bt = BinaryTree() >>> bt = BinaryTree()
@ -49,8 +49,8 @@ class BinaryTree:
>>> bt.insert(2) >>> bt.insert(2)
>>> bt.insert(5) >>> bt.insert(5)
>>> bt.insert(4) >>> bt.insert(4)
>>> bt.morris_inorder_traversal() >>> bt.morris_postorder_traversal()
[2, 3, 4, 5, 6, 7, 9, 10, 12] [2, 4, 5, 3, 7, 6, 12, 10, 9]
""" """
@ -92,9 +92,9 @@ class BinaryTree:
else: else:
self._insert_recursive(node.right, value) self._insert_recursive(node.right, value)
def _predecessor(self, node: TreeNode) -> TreeNode: def _successor(self, node: TreeNode) -> TreeNode:
""" """
Helper Function to return predecessor of the given node in a binary tree Helper Function to return successor of the given node in a binary tree
Parameters: Parameters:
----------- -----------
@ -104,62 +104,64 @@ class BinaryTree:
Returns: Returns:
-------- --------
TreeNode: TreeNode:
The predecessor of the node passed in the parameter The successor of the node passed in the parameter
""" """
temp_node = node.left temp_node = node.right
while temp_node and temp_node.right and temp_node.right != node: while temp_node and temp_node.left and temp_node.left != node:
temp_node = temp_node.right temp_node = temp_node.left
assert temp_node is not None, "Predecessor should not be None" assert temp_node is not None, "Successor should not be None"
return temp_node return temp_node
def morris_inorder_traversal(self) -> list[int]: def morris_postorder_traversal(self) -> list[int]:
""" """
Function for inorder traversal using morris inorder traversal. Function for postorder traversal using morris postorder traversal.
Algorithm : Algorithm :
------------ ------------
First set current node as root node. First set current node as root node.
while current node is not empty while current node is not empty
If the current node has no left child. If the current node has no right child.
print the current node. push the current node to temp.
point the current node to its right child point the current node to its left child
else. else.
find predecssor node of the current node. find successor node of the current node.
if predecessor has no right child, if successor left child points to current node,
make the current node as the right child of the predecessor node. remove the link of the left child of successor node.
point current node to its left child. point the current node to its left child.
else, else,
remove the link of the right child of predecessor node. push the current node to temp.
print the current node make the current node as the left child of the successor node.
point the current node to its right child. point current node to its right child.
Reverse the temp array to get postorder traversaol.
Returns: Returns:
-------- --------
List[int]: List[int]:
A list of integers representing the inorder traversal. A list of integers representing the postorder traversal.
""" """
inorder_traversal = [] postorder_traversal = []
current_node = self.root current_node = self.root
while current_node: while current_node:
if current_node.left is None: if current_node.right is None:
inorder_traversal.append(current_node.value) postorder_traversal.append(current_node.value)
current_node = current_node.right current_node = current_node.left
else: else:
predecessor_node = self._predecessor(current_node) successor_node = self._successor(current_node)
if predecessor_node.right is None: if successor_node.left == current_node:
predecessor_node.right = current_node successor_node.left = current_node
current_node = current_node.left current_node = current_node.left
else: else:
predecessor_node.right = None postorder_traversal.append(current_node.value)
inorder_traversal.append(current_node.value) successor_node.left = current_node
current_node = current_node.right current_node = current_node.right
return inorder_traversal return postorder_traversal[::-1]
if __name__ == "__main__": if __name__ == "__main__":