Added binary tree mirror algorithm (TheAlgorithms#3159)

* Added binary tree mirror algorithm

* Minor changes

* Resolved comments

* Minor Changes

* resolved comments and updated doctests

* updated doctests

* updating DIRECTORY.md

Co-authored-by: svedire <[email protected]>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

Author: 3 people

DIRECTORY.md

@@ -105,6 +105,7 @@
     * [Basic Binary Tree](https://github.com/TheAlgorithms/Python/blob/master/data_structures/binary_tree/basic_binary_tree.py)
     * [Binary Search Tree](https://github.com/TheAlgorithms/Python/blob/master/data_structures/binary_tree/binary_search_tree.py)
     * [Binary Search Tree Recursive](https://github.com/TheAlgorithms/Python/blob/master/data_structures/binary_tree/binary_search_tree_recursive.py)
+    * [Binary Tree Mirror](https://github.com/TheAlgorithms/Python/blob/master/data_structures/binary_tree/binary_tree_mirror.py)
     * [Fenwick Tree](https://github.com/TheAlgorithms/Python/blob/master/data_structures/binary_tree/fenwick_tree.py)
     * [Lazy Segment Tree](https://github.com/TheAlgorithms/Python/blob/master/data_structures/binary_tree/lazy_segment_tree.py)
     * [Lowest Common Ancestor](https://github.com/TheAlgorithms/Python/blob/master/data_structures/binary_tree/lowest_common_ancestor.py)

data_structures/binary_tree/binary_tree_mirror.py

@@ -0,0 +1,44 @@
+"""
+Problem Description:
+Given a binary tree, return it's mirror.
+"""
+
+
+def binary_tree_mirror_dict(binary_tree_mirror_dictionary: dict, root: int):
+    if not root or root not in binary_tree_mirror_dictionary:
+        return
+    left_child, right_child = binary_tree_mirror_dictionary[root][:2]
+    binary_tree_mirror_dictionary[root] = [right_child, left_child]
+    binary_tree_mirror_dict(binary_tree_mirror_dictionary, left_child)
+    binary_tree_mirror_dict(binary_tree_mirror_dictionary, right_child)
+
+
+def binary_tree_mirror(binary_tree: dict, root: int = 1) -> dict:
+    """
+    >>> binary_tree_mirror({ 1: [2,3], 2: [4,5], 3: [6,7], 7: [8,9]}, 1)
+    {1: [3, 2], 2: [5, 4], 3: [7, 6], 7: [9, 8]}
+    >>> binary_tree_mirror({ 1: [2,3], 2: [4,5], 3: [6,7], 4: [10,11]}, 1)
+    {1: [3, 2], 2: [5, 4], 3: [7, 6], 4: [11, 10]}
+    >>> binary_tree_mirror({ 1: [2,3], 2: [4,5], 3: [6,7], 4: [10,11]}, 5)
+    Traceback (most recent call last):
+    ...
+    ValueError: root 5 is not present in the binary_tree
+    >>> binary_tree_mirror({}, 5)
+    Traceback (most recent call last):
+    ...
+    ValueError: binary tree cannot be empty
+    """
+    if not binary_tree:
+        raise ValueError("binary tree cannot be empty")
+    if root not in binary_tree:
+        raise ValueError(f"root {root} is not present in the binary_tree")
+    binary_tree_mirror_dictionary = dict(binary_tree)
+    binary_tree_mirror_dict(binary_tree_mirror_dictionary, root)
+    return binary_tree_mirror_dictionary
+
+
+if __name__ == "__main__":
+    binary_tree = {1: [2, 3], 2: [4, 5], 3: [6, 7], 7: [8, 9]}
+    print(f"Binary tree: {binary_tree}")
+    binary_tree_mirror_dictionary = binary_tree_mirror(binary_tree, 5)
+    print(f"Binary tree mirror: {binary_tree_mirror_dictionary}")