Add remove-nth-node-from-end-of-list solution in TS

Author: Jeehay28

remove-nth-node-from-end-of-list/Jeehay28.ts

@@ -0,0 +1,60 @@
+class ListNode {
+  val: number;
+  next: ListNode | null;
+  constructor(val?: number, next?: ListNode | null) {
+    this.val = val === undefined ? 0 : val;
+    this.next = next === undefined ? null : next;
+  }
+}
+
+// TC: O(n)
+// SC: O(1)
+function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
+  let dummy = new ListNode();
+  dummy.next = head;
+  let fast: ListNode | null = dummy;
+  let slow: ListNode | null = dummy;
+
+  for (let i = 0; i < n + 1; i++) {
+    if (fast) {
+      fast = fast.next;
+    }
+  }
+
+  while (fast) {
+    fast = fast.next;
+    slow = slow!.next;
+  }
+
+  if (slow && slow.next) {
+    slow.next = slow.next.next;
+  }
+
+  return dummy.next;
+}
+
+
+// TC: O(n)
+// SC: O(n)
+// function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
+//   let dummy = head;
+//   const nodes: (ListNode | null)[] = [];
+
+//   while (dummy) {
+//     nodes.push(dummy);
+//     dummy = dummy.next;
+//   }
+
+//   // first node: nodes.length === n
+//   // last node: n === 1
+
+//   if (nodes.length === n) {
+//     head = head!.next;
+//   } else if (nodes.length > 1 && n === 1) {
+//     nodes[nodes.length - 2]!.next = null;
+//   } else {
+//     nodes[nodes.length - n - 1]!.next = nodes[nodes.length - n + 1];
+//   }
+
+//   return head;
+// }