adding algo

src/my_project/interviews/top_150_questions_round_22/ex_63_rotate_linked_list.py

@@ -0,0 +1,42 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+# Definition for singly-linked list.
+class ListNode:
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+class Solution:
+    def rotateRight(self, head: ListNode, k: int) -> ListNode:
+        # Edge cases
+        if not head or not head.next or k == 0:
+            return head
+
+        # Find length and last node
+        length = 1
+        current = head
+        while current.next:
+            current = current.next
+            length += 1
+
+        # Calculate effective rotations
+        k = k % length
+        if k == 0:
+            return head
+
+        # Find new tail (at position length - k - 1)
+        new_tail = head
+        for _ in range(length - k - 1):
+            new_tail = new_tail.next
+
+        # New head is next to new tail
+        new_head = new_tail.next
+
+        # Break the link
+        new_tail.next = None
+
+        # Connect old tail to old head
+        current.next = head
+
+        return new_head

src/my_project/interviews_typescript/top_150_questions_round_1/ex_63_rotate_linked_list.ts

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+import { ListNode } from './ListNode';  
+
+function rotateRight(head: ListNode | null, k: number): ListNode | null {
+    // Edge cases
+    if (!head || !head.next || k === 0) {
+        return head;
+    }
+
+    // Find length and last node
+    let length = 1;
+    let current = head;
+    while (current.next) {
+        current = current.next;
+        length++;
+    }
+
+    // Calculate effective rotations
+    k = k % length;
+    if (k === 0) {
+        return head;
+    }
+
+    // Find new tail (at position length - k - 1)
+    let newTail = head;
+    for (let i = 0; i < length - k - 1; i++) {
+        newTail = newTail.next!;
+    }
+
+    // New head is next to new tail
+    const newHead = newTail.next;
+
+    // Break the link
+    newTail.next = null;
+
+    // Connect old tail to old head
+    current.next = head;
+
+    return newHead;
+}
+

tests/test_150_questions_round_22/test_63_rotate_linked_list_round_22.py

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+import unittest
+from src.my_project.interviews.top_150_questions_round_22\
+.ex_63_rotate_linked_list import Solution, ListNode
+
+class RotateLinkListTestCase(unittest.TestCase):
+
+    def create_linked_list(self, values):
+        """
+        Helper function to create a linked list from a list of values.
+
+        :param values: List of node values
+        :return: Head of the linked list
+        """
+        if not values:
+            return None
+
+        head = ListNode(values[0])
+        current = head
+
+        for val in values[1:]:
+            current.next = ListNode(val)
+            current = current.next
+
+        return head
+
+    def linked_list_to_list(self, head):
+        """
+        Helper function to convert linked list to Python list.
+
+        :param head: Head of the linked list
+        :return: List of values
+        """
+        result = []
+        current = head
+
+        while current:
+            result.append(current.val)
+            current = current.next
+
+        return result
+
+    def test_first_pattern(self):
+        # Example 1: Input: head = [1,2,3,4,5], k = 2
+        # Output: [4,5,1,2,3]
+        solution = Solution()
+        head = self.create_linked_list([1, 2, 3, 4, 5])
+        output = solution.rotateRight(head, 2)
+        result = self.linked_list_to_list(output)
+        target = [4, 5, 1, 2, 3]
+        self.assertEqual(result, target)
+
+    def test_second_pattern(self):
+        # Example 2: Input: head = [0,1,2], k = 4
+        # Output: [2,0,1]
+        solution = Solution()
+        head = self.create_linked_list([0, 1, 2])
+        output = solution.rotateRight(head, 4)
+        result = self.linked_list_to_list(output)
+        target = [2, 0, 1]
+        self.assertEqual(result, target)