Time: 18 ms (27.88%), Space: 90.5 MB (5.31%) - LeetHub

Author: smileeunsong

0234-palindrome-linked-list/0234-palindrome-linked-list-recursive.ts

@@ -0,0 +1,34 @@
+/**
+ * Definition for singly-linked list.
+ * 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 isPalindrome(head: ListNode | null): boolean {
+ let left: ListNode | null = head;
+
+ function dfs(right: ListNode | null): boolean {
+  if (!right) return true;
+
+  // 끝까지 내려가기
+  if (!dfs(right.next)) return false;
+
+  // 돌아오면서 비교
+  // 재귀 패턴: if (!recursiveCall()) return false;
+  // 실패하면 false들고 위로 올라감
+  if (left.val !== right.val) return false;
+
+  // 왼쪽 포인터 이동
+  left = left.next;
+
+  return true;
+ }
+
+ return dfs(head);
+}