src/my_project/interviews/top_150_questions_round_22/ex_61_remove_n_node_from_end_of_list.py

-Original file line number
+Diff line change
@@ -0,0 +1,32 @@
+    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 removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
+            # Create a dummy node to handle edge cases (e.g., removing the head)
+            dummy = ListNode(0)
+            dummy.next = head
+            # Initialize two pointers
+            fast = dummy
+            slow = dummy
+            # Move fast pointer n+1 steps ahead
+            for _ in range(n + 1):
+                fast = fast.next
+            # Move both pointers until fast reaches the end
+            while fast:
+                fast = fast.next
+                slow = slow.next
+            # Skip the nth node from the end
+            slow.next = slow.next.next
+            return dummy.next

...t/interviews_typescript/top_150_questions_round_1/ex_61_remove_n_node_from_end_of_list.ts

-Original file line number
+Diff line change
@@ -0,0 +1,32 @@
+    import { ListNode } from './ListNode';
+    function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
+        // Create a dummy node to handle edge cases (e.g., removing the head)
+        const dummy = new ListNode(0);
+        dummy.next = head;
+        // Initialize two pointers
+        let fast: ListNode | null = dummy;
+        let slow: ListNode | null = dummy;
+        // Move fast pointer n+1 steps ahead
+        for (let i = 0; i < n + 1; i++) {
+            if (fast) {
+                fast = fast.next;
+            }
+        }
+        // Move both pointers until fast reaches the end
+        while (fast !== null) {
+            fast = fast.next;
+            slow = slow!.next;
+        }
+        // Skip the nth node from the end
+        if (slow && slow.next) {
+            slow.next = slow.next.next;
+        }
+        return dummy.next;
+    }

tests/test_150_questions_round_22/test_61_remove_n_node_from_end_of_list_round_22.py

-Original file line number
+Diff line change
@@ -0,0 +1,70 @@
+    import unittest
+    from src.my_project.interviews.top_150_questions_round_22\
+    .ex_61_remove_n_node_from_end_of_list import Solution, ListNode
+    class RemoveNNodeFromEndOfListTestCase(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], n = 2
+            # Output: [1,2,3,5]
+            solution = Solution()
+            head = self.create_linked_list([1, 2, 3, 4, 5])
+            output = solution.removeNthFromEnd(head, 2)
+            result = self.linked_list_to_list(output)
+            target = [1, 2, 3, 5]
+            self.assertEqual(result, target)
+        def test_second_pattern(self):
+            # Example 2: Input: head = [1], n = 1
+            # Output: []
+            solution = Solution()
+            head = self.create_linked_list([1])
+            output = solution.removeNthFromEnd(head, 1)
+            result = self.linked_list_to_list(output)
+            target = []
+            self.assertEqual(result, target)
+        def test_third_pattern(self):
+            # Example 3: Input: head = [1,2], n = 1
+            # Output: [1]
+            solution = Solution()
+            head = self.create_linked_list([1, 2])
+            output = solution.removeNthFromEnd(head, 1)
+            result = self.linked_list_to_list(output)
+            target = [1]
+            self.assertEqual(result, target)

adding algo #1529

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Merged

ivanpenaloza merged 1 commit into main from january27

Jan 27, 2026

-Original file line number
+Diff line change
@@ -0,0 +1,32 @@
+    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 removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
+            # Create a dummy node to handle edge cases (e.g., removing the head)
+            dummy = ListNode(0)
+            dummy.next = head
+            # Initialize two pointers
+            fast = dummy
+            slow = dummy
+            # Move fast pointer n+1 steps ahead
+            for _ in range(n + 1):
+                fast = fast.next
+            # Move both pointers until fast reaches the end
+            while fast:
+                fast = fast.next
+                slow = slow.next
+            # Skip the nth node from the end
+            slow.next = slow.next.next
+            return dummy.next

-Original file line number
+Diff line change
@@ -0,0 +1,32 @@
+    import { ListNode } from './ListNode';
+    function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
+        // Create a dummy node to handle edge cases (e.g., removing the head)
+        const dummy = new ListNode(0);
+        dummy.next = head;
+        // Initialize two pointers
+        let fast: ListNode | null = dummy;
+        let slow: ListNode | null = dummy;
+        // Move fast pointer n+1 steps ahead
+        for (let i = 0; i < n + 1; i++) {
+            if (fast) {
+                fast = fast.next;
+            }
+        }
+        // Move both pointers until fast reaches the end
+        while (fast !== null) {
+            fast = fast.next;
+            slow = slow!.next;
+        }
+        // Skip the nth node from the end
+        if (slow && slow.next) {
+            slow.next = slow.next.next;
+        }
+        return dummy.next;
+    }

-Original file line number
+Diff line change
@@ -0,0 +1,70 @@
+    import unittest
+    from src.my_project.interviews.top_150_questions_round_22\
+    .ex_61_remove_n_node_from_end_of_list import Solution, ListNode
+    class RemoveNNodeFromEndOfListTestCase(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], n = 2
+            # Output: [1,2,3,5]
+            solution = Solution()
+            head = self.create_linked_list([1, 2, 3, 4, 5])
+            output = solution.removeNthFromEnd(head, 2)
+            result = self.linked_list_to_list(output)
+            target = [1, 2, 3, 5]
+            self.assertEqual(result, target)
+        def test_second_pattern(self):
+            # Example 2: Input: head = [1], n = 1
+            # Output: []
+            solution = Solution()
+            head = self.create_linked_list([1])
+            output = solution.removeNthFromEnd(head, 1)
+            result = self.linked_list_to_list(output)
+            target = []
+            self.assertEqual(result, target)
+        def test_third_pattern(self):
+            # Example 3: Input: head = [1,2], n = 1
+            # Output: [1]
+            solution = Solution()
+            head = self.create_linked_list([1, 2])
+            output = solution.removeNthFromEnd(head, 1)
+            result = self.linked_list_to_list(output)
+            target = [1]
+            self.assertEqual(result, target)

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