Leetcode 234. Palindrome Linked List

文章作者：Tyan
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1. Description

Palindrome Linked List

2. Solution

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    bool isPalindrome(ListNode* head) {
        if(!head || !head->next) {
            return true;
        }
        ListNode* current = head;
        ListNode* mid = head;
        while(current && current->next) {
            mid = mid->next;
            current = current->next->next;
        }
        ListNode* pre = mid;
        current = mid->next;
        mid->next = nullptr;
        ListNode* next = nullptr;
        while(current) {
            next = current->next;
            current->next = pre;
            pre = current;
            current = next;
        }
        current = head;
        while(pre) {
            if(pre->val != current->val) {
                return false;
            }
            pre = pre->next;
            current = current->next;
        }
        return true;
    }
};

Reference

1. https://leetcode.com/problems/palindrome-linked-list/description/