【leetcode 简单】 第六十题 反转链表

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* reverseList(struct ListNode* head) {
    if (NULL == head || NULL == head->next)
    {
        return head;
    }
    struct ListNode* a=head;
    struct ListNode* b=head->next;
    struct ListNode* c;
    
    head->next = NULL;
    while (b)
    {
        c = b->next;
        b->next = a;
        a = b;
        b = c;
    }
    head = a;
    return head;
}