C++ 解法, 执行用时: 1ms, 内存消耗: 628KB, 提交时间: 2017-10-04

class PalindromeList {
public:
    bool chkPalindrome(ListNode* A) {
        // write code here
        if(A==NULL)
            return false;
        else if(A->next==NULL)
            return true;
        //快慢指针找出中间节点
        ListNode* quick=A;
        ListNode* slow=A;
        while(quick!=NULL&&quick->next!=NULL)
        {
            quick=quick->next->next;
            slow=slow->next;
        }
        //反转
        ListNode* p=slow->next;
        ListNode* p1=p->next;       
        while(p!=NULL)
        {
            p->next=slow;
            slow=p;
            p=p1;
            p1=p1->next;
        }
         
        while(A!=slow)
        {
            if((A->val)!=(slow->val))
            {
                return false;
            }else{
                if(A->next==slow)
                {
                    return true;
                }
                A=A->next;
                slow=slow->next;
            }
        }
        return true;
         
    }
};

C++ 解法, 执行用时: 2ms, 内存消耗: 688KB, 提交时间: 2021-07-26

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};*/
class PalindromeList {
public:
    bool chkPalindrome(ListNode* A) {
        // write code here
        if( A == NULL || A->next==NULL)
            return true;
        //找到中间节点
        struct ListNode* fast,*slow;
        fast = slow = A;
        while(fast && fast->next)
        {
            fast=fast->next->next;
            slow=slow->next;
        }
        //头插进行逆转
        struct ListNode* newHead = NULL;
        struct ListNode* cur = slow;
        while(cur)
        {
            struct ListNode* next =cur->next;
            cur->next = newHead;
            newHead = cur;
            //更新cur
            cur=next;
        }
        //同时遍历
        while(A && newHead)
        {
            if(A->val != newHead->val)
                return false;       //只要有一个不同，就不是  回文
            A = A->next;
            newHead = newHead->next;
            
        }
        //循环结束，都相同，说明是回文
        return true;
    }
};