LeetCode 206: Reverse Linked List

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
	ListNode* reverseList(ListNode* head) {
		ListNode *pre = NULL, *now = head, *nxt = NULL;

		while (now != NULL) {
			nxt = now->next;
			now->next = pre;
			pre = now;
			now = nxt;
		}
		return pre;
	}
};