剑指Offer——删除链表中重复的结点

import java.util.HashMap;
public class Solution {
    public ListNode deleteDuplication(ListNode pHead)
    {
     //1、临界值的判断：
        if (pHead == null) {
            return null;
        }
        HashMap<Integer, Integer> hashMap = new HashMap<>();
        ListNode temp = pHead;
        while (temp != null) {
            if (hashMap.containsKey(temp.val) == true) {
                hashMap.put(temp.val, hashMap.get(temp.val) + 1);
            } else {
                hashMap.put(temp.val, 1);
            }
            temp = temp.next;
        }
        temp = pHead;
        ListNode newHead = new ListNode(-1);
        ListNode NTemp = newHead;
        while (temp != null) {
            if (hashMap.get(temp.val) > 1) {
                temp = temp.next;
            } else {
                NTemp.next = new ListNode(temp.val);
                NTemp = NTemp.next;
                temp = temp.next;
            }
        }
        return newHead.next;
    }
}