[ PS ] : Remove Nth Node From End of List

Author: uraflower

remove-nth-node-from-end-of-list/uraflower.js

@@ -0,0 +1,59 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+
+// 첫 번째 풀이
+// 시간복잡도: O(n)
+// 공간복잡도: O(n)
+/**
+ * @param {ListNode} head
+ * @param {number} n
+ * @return {ListNode}
+ */
+const removeNthFromEnd = function (head, n) {
+    function dfs(node) {
+        // 마지막 노드이면 1 반환
+        if (!node.next) {
+            return 1;
+        }
+
+        const nth = dfs(node.next);
+        if (nth === n) {
+            node.next = node.next.next ?? null;
+        }
+
+        return nth + 1;
+    }
+
+    if (dfs(head) === n) {
+        return head.next;
+    }
+
+    return head;
+};
+
+// 두 번째 풀이
+// 시간복잡도: O(n)
+// 공간복잡도: O(1)
+const removeNthFromEnd = function (head, n) {
+    const temp = new ListNode(0, head);
+    let tail = temp; 
+    let prev = temp; // 뒤에서 n번째 노드
+    
+    for (let i = 0; i < n; i++) {
+        tail = tail.next;
+    }
+
+    while (tail.next) {
+        tail = tail.next;
+        prev = prev.next;
+    }
+    
+    prev.next = prev.next.next;
+
+    return temp.next;
+};