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* p = head;
    struct ListNode* q = p -> next;
    struct ListNode* t = q -> next;
    head -> next = NULL;
    if(t == NULL){
        q -> next = p;
    }
    while(t != NULL) {
        q -> next = p;
        p = q;
        q = t;
        t = q -> next;
    }
    q -> next = p;
    return  q; 
}