Feat: 19. Remove Nth Node From End of List

Author: HC-kang

remove-nth-node-from-end-of-list/HC-kang.ts

@@ -0,0 +1,33 @@
+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;
+  }
+}
+
+/**
+ * https://leetcode.com/problems/remove-nth-node-from-end-of-list
+ * T.C. O(N)
+ * S.C. O(1)
+ */
+function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
+  let first = head;
+  let second = head;
+
+  for (let i = 0; i < n; i++)
+    first = first!.next;
+
+  if (!first)
+    return head!.next;
+
+  while (first.next) {
+    first = first.next;
+    second = second!.next;
+  }
+
+  second!.next = second!.next!.next;
+
+  return head;
+}