leetcode_palindrome_linked_list

发表于

难度：Easy

解题思路：先找到链表中间节点，然后切段，然后把后一段翻转，最后对比。

代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
/**
 * 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) {
        ListNode *dummy = new ListNode(-1);
        dummy->next = head;
        ListNode *slow = dummy;
        ListNode *fast = dummy;
        while(fast->next != NULL && fast->next->next != NULL)
        {
            slow = slow->next;
            fast = fast->next->next;
        }
        ListNode *new_head = NULL;
        if(fast->next != NULL)
        {
            new_head = slow->next->next;
            slow->next = NULL;
        }
        else
        {
            new_head = slow->next;
            slow->next = NULL;
        }
        new_head = reverseList(new_head);
        ListNode *first_cur = dummy->next;
        ListNode *second_cur = new_head;
        while(first_cur != NULL && second_cur != NULL)
        {
            if(first_cur->val != second_cur->val)
                return false;
            else
            {
                first_cur=first_cur->next;
                second_cur = second_cur->next;
            }
        }
        return true;

    }
    ListNode* reverseList(ListNode* head) {
        ListNode* pre = NULL;
        ListNode* cur = head;
        while(cur != NULL)
        {
            ListNode *ne = cur->next;
            cur->next = pre;
            pre = cur;
            cur = ne;
        }
        return pre;
    }
};

运行结果：23ms，超过56.02%