反轉一個單鏈表。
示例:
輸入: 1->2->3->4->5->NULL 輸出: 5->4->3->2->1->NULL
//非遞歸
public ListNode reverseList(ListNode head) {
ListNode prev = null;
ListNode curr = head;
while (curr != null) {
ListNode nextTemp = curr.next;
curr.next = prev;
prev = curr;
curr = nextTemp;
}
return prev;
}
//遞歸(太騷了)
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;
}