题解 | #判断一个链表是否为回文结构#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 the head
 * @return bool布尔型
 */
bool isPail(struct ListNode* head ) {
    // write code here
    if(head == NULL) return false;
    if(head->next == NULL) return true;

    struct ListNode *slow = head, *fast = head, *prev = NULL;
    while(fast && fast->next) {
        fast = fast->next->next;
        struct ListNode *next_slow = slow->next;
        slow->next = prev;
        prev = slow;
        slow = next_slow;
    }
    if(fast != NULL) {
        slow = slow->next;
    }
    while(slow != NULL) {
        if(slow->val != prev->val) {
            return false;
        }
        slow = slow->next;
        prev = prev->next;
    }
    return true;
}