Merge branch 'TheAlgorithms:master' into master

ciphers/gronsfeld_cipher.py

@@ -0,0 +1,45 @@
+from string import ascii_uppercase
+
+
+def gronsfeld(text: str, key: str) -> str:
+    """
+    Encrypt plaintext with the Gronsfeld cipher
+
+    >>> gronsfeld('hello', '412')
+    'LFNPP'
+    >>> gronsfeld('hello', '123')
+    'IGOMQ'
+    >>> gronsfeld('', '123')
+    ''
+    >>> gronsfeld('yes, ¥€$ - _!@#%?', '0')
+    'YES, ¥€$ - _!@#%?'
+    >>> gronsfeld('yes, ¥€$ - _!@#%?', '01')
+    'YFS, ¥€$ - _!@#%?'
+    >>> gronsfeld('yes, ¥€$ - _!@#%?', '012')
+    'YFU, ¥€$ - _!@#%?'
+    >>> gronsfeld('yes, ¥€$ - _!@#%?', '')
+    Traceback (most recent call last):
+      ...
+    ZeroDivisionError: integer modulo by zero
+    """
+    ascii_len = len(ascii_uppercase)
+    key_len = len(key)
+    encrypted_text = ""
+    keys = [int(char) for char in key]
+    upper_case_text = text.upper()
+
+    for i, char in enumerate(upper_case_text):
+        if char in ascii_uppercase:
+            new_position = (ascii_uppercase.index(char) + keys[i % key_len]) % ascii_len
+            shifted_letter = ascii_uppercase[new_position]
+            encrypted_text += shifted_letter
+        else:
+            encrypted_text += char
+
+    return encrypted_text
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()

data_structures/binary_tree/maximum_sum_bst.py

@@ -0,0 +1,78 @@
+from __future__ import annotations
+
+import sys
+from dataclasses import dataclass
+
+INT_MIN = -sys.maxsize + 1
+INT_MAX = sys.maxsize - 1
+
+
+@dataclass
+class TreeNode:
+    val: int = 0
+    left: TreeNode | None = None
+    right: TreeNode | None = None
+
+
+def max_sum_bst(root: TreeNode | None) -> int:
+    """
+    The solution traverses a binary tree to find the maximum sum of
+    keys in any subtree that is a Binary Search Tree (BST). It uses
+    recursion to validate BST properties and calculates sums, returning
+    the highest sum found among all valid BST subtrees.
+
+    >>> t1 = TreeNode(4)
+    >>> t1.left = TreeNode(3)
+    >>> t1.left.left = TreeNode(1)
+    >>> t1.left.right = TreeNode(2)
+    >>> print(max_sum_bst(t1))
+    2
+    >>> t2 = TreeNode(-4)
+    >>> t2.left = TreeNode(-2)
+    >>> t2.right = TreeNode(-5)
+    >>> print(max_sum_bst(t2))
+    0
+    >>> t3 = TreeNode(1)
+    >>> t3.left = TreeNode(4)
+    >>> t3.left.left = TreeNode(2)
+    >>> t3.left.right = TreeNode(4)
+    >>> t3.right = TreeNode(3)
+    >>> t3.right.left = TreeNode(2)
+    >>> t3.right.right = TreeNode(5)
+    >>> t3.right.right.left = TreeNode(4)
+    >>> t3.right.right.right = TreeNode(6)
+    >>> print(max_sum_bst(t3))
+    20
+    """
+    ans: int = 0
+
+    def solver(node: TreeNode | None) -> tuple[bool, int, int, int]:
+        """
+        Returns the maximum sum by making recursive calls
+        >>> t1 = TreeNode(1)
+        >>> print(solver(t1))
+        1
+        """
+        nonlocal ans
+
+        if not node:
+            return True, INT_MAX, INT_MIN, 0  # Valid BST, min, max, sum
+
+        is_left_valid, min_left, max_left, sum_left = solver(node.left)
+        is_right_valid, min_right, max_right, sum_right = solver(node.right)
+
+        if is_left_valid and is_right_valid and max_left < node.val < min_right:
+            total_sum = sum_left + sum_right + node.val
+            ans = max(ans, total_sum)
+            return True, min(min_left, node.val), max(max_right, node.val), total_sum
+
+        return False, -1, -1, -1  # Not a valid BST
+
+    solver(root)
+    return ans
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()