feat: add Remove Nth Node From End of List

Author: dukeluo

README.md

@@ -40,6 +40,7 @@ https://neetcode.io/roadmap
 | 206 | [Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/)                                                       | Easy       | [ts](./TypeScript/206.reverse-linked-list.ts) [rkt](./Racket/206.reverse-linked-list.rkt)     | Linked List      |
 | 21  | [Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/)                                                 | Easy       | [ts](./TypeScript/21.merge-two-sorted-lists.ts) [rkt](./Racket/21.merge-two-sorted-lists.rkt) | Linked List      |
 | 143 | [Reorder List](https://leetcode.com/problems/reorder-list/)                                                                     | Medium     | [ts](./TypeScript/143.reorder-list.ts)                                                        | Linked List      |
+| 19  | [Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/)                             | Medium     | [ts](./TypeScript/19.remove-nth-node-from-end-of-list.ts)                                     | Linked List      |
 
 ### Others
 

TypeScript/19.remove-nth-node-from-end-of-list.ts

@@ -0,0 +1,27 @@
+interface ListNode {
+  val: number;
+  next: ListNode | null;
+}
+
+function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
+  let dummy: ListNode = {
+    val: -1,
+    next: head,
+  };
+  let slow: ListNode | null | undefined = dummy;
+  let fast: ListNode | null | undefined = head;
+
+  while (n > 0) {
+    fast = fast?.next;
+    n--;
+  }
+  while (fast) {
+    slow = slow?.next;
+    fast = fast.next;
+  }
+  if (slow && slow.next) {
+    slow.next = slow.next.next;
+  }
+
+  return dummy.next;
+}