feat: solve #248 with python

Author: EgonD3V

remove-nth-node-from-end-of-list/EGON.py

@@ -0,0 +1,91 @@
+from typing import Optional
+from unittest import TestCase, main
+
+
+# Definition for singly-linked list.
+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+
+    def values(self) -> [int]:
+        result = []
+        node = self
+        while node:
+            result.append(node.val)
+            node = node.next
+
+        return result
+
+
+class Solution:
+    def removeNthFromEnd(self, head: Optional[ListNode], n: int) -> Optional[ListNode]:
+        return self.solve_two_pointer(head, n)
+    """
+    Runtime: 0 ms (Beats 100.00%)
+    Time Complexity: O(n)
+    > list의 모든 node + dummy node를 탐색하므로 O(n + 1) ~= O(n)
+
+    Memory: 16.62 MB (Beats 15.78%)
+    Space Complexity: O(1)
+    > 포인터만 사용하므로 O(1)
+    """
+    def solve_two_pointer(self, head: Optional[ListNode], n: int) -> Optional[ListNode]:
+        if head.next is None:
+            return None
+
+        dummy = ListNode(-1)
+        dummy.next = head
+        head = dummy
+
+        slow = fast = head
+        while n:
+            if fast.next:
+                fast = fast.next
+            n -= 1
+
+        while fast is not None:
+            if fast.next is None:
+                slow.next = slow.next.next
+                break
+            else:
+                slow = slow.next
+                fast = fast.next
+
+        return head.next
+
+
+class _LeetCodeTestCases(TestCase):
+    def test_1(self):
+        node_1 = ListNode(1)
+        node_2 = ListNode(2)
+        node_3 = ListNode(3)
+        node_4 = ListNode(4)
+        node_5 = ListNode(5)
+
+        node_1.next = node_2
+        node_2.next = node_3
+        node_3.next = node_4
+        node_4.next = node_5
+
+        n = 2
+        output = [1, 2, 3, 5]
+        self.assertEqual(Solution().removeNthFromEnd(node_1, n).values(), output)
+
+    def test_2(self):
+        node_1 = ListNode(1)
+        n = 1
+        output = []
+        self.assertEqual(Solution().removeNthFromEnd(node_1, n).values(), output)
+
+    def test_3(self):
+        node_1 = ListNode(1)
+        node_2 = ListNode(2)
+        node_1.next = node_2
+        n = 2
+        output = [2]
+        self.assertEqual(Solution().removeNthFromEnd(node_1, n).values(), output)
+
+
+if __name__ == '__main__':
+    main()