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# 82.Remove-Duplicates-from-Sorted-List-II

## 82. Remove Duplicates from Sorted List II

## 题目地址

<https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/>

<https://www.lintcode.com/problem/remove-duplicates-from-sorted-list-ii/description>

## 题目描述

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

Return the linked list sorted as well.

Example 1:
Input: 1->2->3->3->4->4->5
Output: 1->2->5

Example 2:
Input: 1->1->1->2->3
Output: 2->3
```

## 代码

### Approach #1 Two while-loop

```java
public class Solution {
    public ListNode deleteDuplicates(ListNode head){
    if (head == null)     return null;

    ListNode dummy = new ListNode(0);
    dummy.next = head;
    ListNode node = dummy;
    while (node.next != null && node.next.next != null) {
      if (node.next.val == node.next.next.val) {
        int val_prev = node.next.val;
        while (node.next != null && node.next.val == val_prev) {
          node.next = node.next.next;
        }
      } else {
        node = node.next;
      }
    }

    return dummy.next;
  }
}
```


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