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:
    //返回中间节点
    struct ListNode* middleNode(struct ListNode* head) {
    //快慢指针问题
    struct ListNode* slow, *fast;
    slow = fast = head;
    while(fast && fast->next)
    {
        slow = slow->next;
        fast = fast->next->next;
    }
    return slow;
}
    //逆置
    struct ListNode* reverseList(struct ListNode* head) {
    struct ListNode* cur = head;
    struct ListNode* newhead = NULL;
    while(cur)
    {
        struct ListNode* next = cur->next;
        //头插
        cur->next = newhead;
        newhead = cur;
        cur = next; 
    }
    return newhead;
}
    bool chkPalindrome(ListNode* A) {
        // write code here
        struct ListNode* mid = middleNode(A);
        struct ListNode* rHead = reverseList(mid);
        while(A && rHead)
        {
            if(A->val == rHead->val)
            {
                    A = A->next;
                    rHead = rHead->next;
            }
            else
            {
                return false;
            }
        }
        return true;
    }
};