206. Reverse Linked List
Reverse a singly linked list. Example
Input: 1->2->3->4->5->NULL
Output: 5->4->3->2->1->NULL
题意：如题目所讲。反转链表。这个是链表题中的重中之重。
代码
class Solution {
public ListNode reverseList(ListNode head) {
if(head == null) return null;
ListNode prev = null, next = null, cur = head;
while(cur != null) {
next = cur.next;
cur.next = prev;
prev = cur;
cur = next;
}
return prev;
}
}
Recursion 版本
public ListNode reverseList(ListNode head) {
if (head == null || head.next == null) return head;
ListNode p = reverseList(head.next);
head.next.next = head;
head.next = null;
return p;
}