0234-palindrome-linked-list.js

// 234. Palindrome Linked List
// Easy   33%

// Given a singly linked list, determine if it is a palindrome.

// Follow up:
// Could you do it in O(n) time and O(1) space?


/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} head
 * @return {boolean}
 */
const isPalindrome = function(head) {
  function iter(node) {
    let result = node.next ? iter(node.next) : true
    if (head.val === node.val) {
      head = head.next
      return result
    } else return false
  }
  return head ? iter(head) : true
}

const ListNode = require('../structs/ListNode')
;[
  [1,2,3,4,5,4,3,2,1],  // true
  [1,2,3,3,2,1],        // true
  [1,2,3,4,3,2,0,1],    // false
].forEach((array) => {
  console.log(isPalindrome(ListNode.from(array)))
})

// Solution:
// 利用函数的堆栈来实现一般的堆栈。


// Submission Result: Accepted