deleteDuplicates

给定一个排序链表，删除所有重复的元素，使得每个元素只出现一次。

示例 1:

输入: 1->1->2
输出: 1->2
示例 2:

输入: 1->1->2->3->3
输出: 1->2->3

class ListNode {
      int val;
      ListNode next;
      ListNode(int x) { val = x; }
}
// 非递归解法
public class deleteDuplicates {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode node = head;
        while(head != null && head.next != null){
            if(head.next.val == head.val){
                ListNode listNode = head.next;
                head.next = listNode.next;
            }
            head = head.next;
        }
        return node;
    }
}