Time: 2 ms (99.56%), Space: 78.7 MB (58.19%) - LeetHub

Author: smileeunsong

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

@@ -0,0 +1,48 @@
+/**
+ * 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)
+ *     }
+ * }
+ */
+
+// 연결 리스트 팰린드롬 공식 = 중간 찾고 + 뒤집고 + 마주보기
+function isPalindrome(head: ListNode | null): boolean {
+    if (!head || !head.next) return true;
+
+    // 1. 중간 찾기
+    let slow: ListNode | null = head;
+    let fast: ListNode | null = head;
+    
+    while (fast && fast.next) {
+        slow = slow.next;
+        fast = fast.next.next;
+    }
+
+    // 2. 뒤 절반 뒤집기
+    let prev: ListNode | null = null;
+    let curr: ListNode | null = slow;
+
+    while (curr) {
+        const next = curr.next;
+        curr.next = prev;
+        prev = curr;
+        curr = next;
+    }
+
+    // 3. 앞쪽과 비교
+    let left: ListNode | null = head;
+    let right: ListNode | null = prev;
+
+    while (right) {
+        if (left.val !== right.val) return false;
+        left = left.next;
+        right = right.next;
+    }
+
+    return true;
+}