add Remove Nth Node From End of List solution

Author: HoonDongKang

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

@@ -0,0 +1,58 @@
+/**
+ * [Problem]: [19] Remove Nth Node From End of List
+ * (https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/)
+ */
+
+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;
+    }
+}
+
+function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
+    // 시간복잡도 O(N)
+    // 공간복잡도 O(1)
+    function lengthFunc(head: ListNode | null, n: number): ListNode | null {
+        let length = 0;
+        let current = head;
+        while (current) {
+            length++;
+            current = current.next;
+        }
+
+        let dummy = new ListNode(0, head);
+        current = dummy;
+
+        for (let i = 0; i < length - n; i++) {
+            current = current?.next!;
+        }
+
+        current.next = current.next!.next || null;
+
+        return dummy.next;
+    }
+
+    // 시간복잡도 O(N)
+    // 공간복잡도 O(1)
+    function twoPointerFunc(head: ListNode | null, n: number): ListNode | null {
+        let first = head;
+
+        for (let i = 0; i < n; i++) {
+            first = first?.next!;
+        }
+
+        let dummy = new ListNode(0, head);
+        let second = dummy;
+
+        while (first) {
+            first = first.next;
+            second = second.next!;
+        }
+
+        second.next = second.next?.next || null;
+        return dummy.next;
+    }
+}