```import java.util.*;
/*
* public class ListNode {
* int val;
* ListNode next = null;
* }
*/
public class Solution {
/**
*
* @param head ListNode类
* @return ListNode类
*/
public ListNode deleteDuplicates (ListNode head) {
// write code here
if(head == null) return null;
ListNode fast = head;
while(fast.next != null) {
if (fast.val == fast.next.val) {
fast.next = fast.next.next;
} else {
fast = fast.next;
}
}
return head;
}
}