反转链表的Java实现
1. 题目
反转链表，例如，原链表1-2-3-4-5，反转后为5-4-3-2-1。
2. 迭代法实现
private ListNode reverseList(ListNode head) {
if(head == null || head.next == null){
return head;
}
ListNode cur = head.next;
head.next = null;
while(cur != null){
ListNode next = cur.next;
cur.next = head;
head = cur;
cur = next;
}
return head;
}
3. 头插法实现
private static ListNode reverseList(ListNode head) {
if(head == null || head.next == null){
return head;
}
ListNode newHead = new ListNode(0);
while(head != null){
ListNode next = head.next;
head.next = newHead.next;
newHead.next = head;
head = next;
}
return newHead.next;
}