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 || head->next == NULL) {
        return head;
    }
    struct ListNode * beg = NULL;
    struct ListNode * end = head->next;
    while(1) {
        head->next = beg;//关键步骤，next的赋值
        if (end == NULL) {
            break;
        }
        beg = head;
        head = end;
        end = end->next;
        
    }
    return head;
}