LeetCode 82. Remove Duplicates from Sorted List II

82. Remove Duplicates from Sorted List II

Difficulty: Medium

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

Example 1:

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

Example 2:

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

Solution

Language: Java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if (head == null) {
            return null;
        }
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode prev = dummy;
        int cur = 0;
        while(head != null) {
            if (head.next != null && head.val == head.next.val) {
                cur = head.val;
                while (head != null && head.val == cur) {
                    head = head.next;
                }
                prev.next = head;
            } else {
                prev = head;
                head = head.next;
            }
        }
        return dummy.next;
    }
}