adding algo

Author: ivanpenaloza

src/my_project/interviews/top_150_questions_round_22/ex_64_partition_linked_list.py

@@ -0,0 +1,41 @@
+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 partition(self, head: Optional[ListNode], x: int) -> Optional[ListNode]:
+        # Create two dummy nodes for the two partitions
+        less_dummy = ListNode(0)
+        greater_dummy = ListNode(0)
+        
+        # Pointers to build the two lists
+        less = less_dummy
+        greater = greater_dummy
+        
+        # Traverse the original list
+        current = head
+        while current:
+            if current.val < x:
+                # Add to the "less than" list
+                less.next = current
+                less = less.next
+            else:
+                # Add to the "greater or equal" list
+                greater.next = current
+                greater = greater.next
+            current = current.next
+        
+        # Important: Set the end of greater list to None
+        # to avoid cycles
+        greater.next = None
+        
+        # Connect the two lists
+        less.next = greater_dummy.next
+        
+        # Return the head of the combined list
+        return less_dummy.next

src/my_project/interviews_typescript/top_150_questions_round_1/ex_64_partition_linked_list.ts

@@ -0,0 +1,37 @@
+import { ListNode } from './ListNode';  
+
+function partition(head: ListNode | null, x: number): ListNode | null {
+    // Create two dummy nodes for the two partitions
+    const lessDummy = new ListNode(0);
+    const greaterDummy = new ListNode(0);
+    
+    // Pointers to build the two lists
+    let less = lessDummy;
+    let greater = greaterDummy;
+    
+    // Traverse the original list
+    let current = head;
+    while (current !== null) {
+        if (current.val < x) {
+            // Add to the "less than" list
+            less.next = current;
+            less = less.next;
+        } else {
+            // Add to the "greater or equal" list
+            greater.next = current;
+            greater = greater.next;
+        }
+        current = current.next;
+    }
+    
+    // Important: Set the end of greater list to null
+    // to avoid cycles
+    greater.next = null;
+    
+    // Connect the two lists
+    less.next = greaterDummy.next;
+    
+    // Return the head of the combined list
+    return lessDummy.next;
+}
+

tests/test_150_questions_round_22/test_64_partition_linked_list_round_22.py

@@ -0,0 +1,60 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_22\
+.ex_64_partition_linked_list import Solution, ListNode
+
+class PartitionLinkedListTestCase(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 = [1,4,3,2,5,2], x = 3
+        # Output: [1,2,2,4,3,5]
+        solution = Solution()
+        head = self.create_linked_list([1, 4, 3, 2, 5, 2])
+        output = solution.partition(head, 3)
+        result = self.linked_list_to_list(output)
+        target = [1, 2, 2, 4, 3, 5]
+        self.assertEqual(result, target)
+
+    def test_second_pattern(self):
+        # Example 2: Input: head = [2,1], x = 2
+        # Output: [1,2]
+        solution = Solution()
+        head = self.create_linked_list([2, 1])
+        output = solution.partition(head, 2)
+        result = self.linked_list_to_list(output)
+        target = [1, 2]
+        self.assertEqual(result, target)