Leetcode-234. 回文链表

/**
 * 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) {
        bool ans = deduce(head);
        return ans;
    }
    bool deduce(ListNode* head)
    {
        vector<int> vec;
        vec.clear();
        
        while (head!= NULL)
        {
            vec.push_back(head->val);
            head = head->next;
        }
        
        int len = vec.size();
        for (int i = 0, j = len-1; i<=j; i++, j--) /*因为len可能是奇数，所以i<=j;*/
        {
            if (vec[i]!= vec[j]) return false;
        }
        return true;
    }
};