LeetCode206反转链表

反转一个单链表。

示例:

输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* reverseList(struct ListNode* head) {
    if(head == NULL || head -> next == NULL)
        return head;
    struct ListNode *pre, *cur;
    pre = NULL;
    cur = head;
    while(cur != NULL){
        struct ListNode *nex;
        nex = cur -> next;
        cur -> next = pre;
        pre = cur;
        cur = nex;
    }
    return pre;
}