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
 */
#include <stdlib.h>
struct ListNode* ReverseList(struct ListNode* head ) {
    if (head == NULL || head->next == NULL) {
        return head;
    }
    struct ListNode* head_next1 = head->next;
    struct ListNode* head_next2 = head->next->next;
    head->next = NULL;
    while (head_next2 != NULL) {
        head_next1->next = head;
        head = head_next1;
        head_next1 = head_next2;
        head_next2 = head_next2->next;
    }
    head_next1->next = head;
    head = head_next1;
    return head;
    // write code here
}