题解 | #反转链表#

/**
 * 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 
 * @return ListNode类
 */
struct ListNode* ReverseList(struct ListNode* head ) {
    // write code here
    if(head == NULL)
    {
        return NULL;
    }
    if(head->next == NULL)
    {
        return head;
    }
    struct ListNode* first = head;
    struct ListNode* last = head;
    head = first->next;
    last = head->next;
    first->next = NULL;
    while(head->next)
    {
        last = head->next;
        head->next = first;
        first = head;
        head = last;
    }
    head->next = first;
    return head;
}