題目描述
在一個排序的鏈表中，存在重復的結(jié)點，請刪除該鏈表中重復的結(jié)點，重復的結(jié)點不保留，返回鏈表頭指針。 例如，鏈表1->2->3->3->4->4->5 處理后為 1->2->5

import java.util.HashSet;
import java.util.Set;

public class Solution {
    
    public ListNode deleteDuplication(ListNode pHead) {
        
        if(pHead == null)
            return null;
        ListNode node = pHead;
        ListNode pre = pHead;
        Set<Integer> set = new HashSet<Integer>();
        Set<Integer> set1 = new HashSet<Integer>();
        while(node != null) {
            
            if(set.contains(node.val)) {
                set1.add(node.val);
                pre.next = node.next;
                node = node.next;
            }else {
                
                set.add(node.val);
                pre = node;
                node = node.next;
            }
        }
        node = pHead;
        pre = pHead;
        while(node != null) {
            
            if(set1.contains(node.val)) {
                
                if(node == pHead) {
                    
                    pHead = pHead.next;
                    node = pHead;
                    pre = pHead;
                }else {
                    
                    pre.next = node.next;
                    node = node.next;
                }
            }else {
                
                pre = node;
                node = node.next;
            }
        }
        return pHead;
    }
}