LeetCode OJ 82. 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.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

相对于Remove Duplicates from Sorted List这个问题，这个问题是要把重复出现过的所有元素全部删除。我的想法是找出每一个数字段的起点和终点，如果这个数据段出现了重复元素，就把这个数据段整体删除。

public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if(head==null || head.next==null) return head;
        ListNode thead = new ListNode(-1);
        ListNode begin = thead;
        ListNode end = head;
        thead.next = head;
        
        int cur = head.val;
        while(end.next!=null){
            if(end.next.val==cur){
                end = end.next;
            }
            else{
                if(begin.next==end){
                    begin = end;
                    end = end.next;
                }
                else{
                    begin.next = end.next;
                    end = begin.next;
                }
                cur = end.val;
            }
        }
        if(begin.next==end) return thead.next;
        begin.next = null;
        return thead.next;
    }
}