题解 | #判断一个链表是否为回文结构#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */

/**
 * 
 * @param head ListNode类 the head
 * @return bool布尔型
 */
bool isPail(struct ListNode* head ) {
    // write code here
    struct ListNode* p1 = head;//快指针
    struct ListNode* p2 = head;//慢指针
    struct ListNode* n = NULL;
    if(NULL == head || NULL == head->next)    return true;
    while(NULL!=p1 && NULL!=p1->next)
    {
        p1 = p1->next->next;
        p2 = p2->next;
    }
    p1 = p2->next;
    p2->next = NULL;
    while(NULL != p1)
    {
        n = p1->next;
        p1->next = p2;
        p2 = p1;
        p1 = n;
    }
    p1 = head;
    while(NULL!=p1 && NULL!=p2)
    {
        if(p1->val != p2->val)    return false;
        p1 = p1->next;
        p2 = p2->next;
    }
    return true;
}