双指针

alt

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 i = head,j = head;
        while(i != null && j != null){
            if(i.val != j.val){
                i.next = j;
                i = i.next;
            }
                j = j.next;
        }
        i.next = null;
        return head;
    }
}