Remove Duplicates from Sorted List II

Source

• lintcode: Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have
duplicate numbers, leaving only distinct numbers from the original list.

Example
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

Java

/**
 * Definition for ListNode
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param ListNode head is the head of the linked list
     * @return: ListNode head of the linked list
     */
    public static ListNode deleteDuplicates(ListNode head) {
        ListNode dummy = new ListNode(0);  
        dummy.next = head;  
        ListNode pre = dummy;  
        ListNode cur = head;  

        //要同时check cur 和 cur.next 是不是null  
        while(cur!=null && cur.next!=null){  
            if(cur.val!=cur.next.val){  
                pre=pre.next;  
                cur=cur.next; 
            }  
            else{  
                while(cur.next!=null && cur.val==cur.next.val){  
                    cur=cur.next;  
                }  
                pre.next=cur.next;  
                cur=cur.next; 
            }  
        }     
        return dummy.next;  
    }
}