题解 | #链表的回文结构#

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};*/
class PalindromeList {
public:
    bool chkPalindrome(ListNode* A) {
        // write code here
        struct ListNode* slow,*fast,*mid,*cur,*insertnode,*head;
        slow=fast=A;
        mid=insertnode=head=NULL;
        //找中间节点
        while(fast&&fast->next)
        //cur->next判断奇数链表尾，cur判断偶数链表尾
        {
            slow=slow->next;
            fast=fast->next->next;
        }
        mid=slow;

        //mid把原始链表分为左链表，右链表（包括mid）
        //逆转右链表
        cur=mid->next;
        head=mid;
        while(cur)
        {
            //头插,将cur插入head前，并后置cur
            insertnode=cur;
            cur=cur->next;
            insertnode->next=head;
            head=insertnode;
        }
        mid->next=NULL;

        //开始比较
        while(A&&head)
        {
            if(A->val!=head->val)
            {
                return false;
            }
            else
            {
                A=A->next;
                head=head->next;
            }
        }
        return true;
    }
};