0082 - Remove Duplicates from Sorted List II

0082 - Remove Duplicates from Sorted List II

Given the head of 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.

Examples

Input: head = [1,2,3,3,4,4,5] Output: [1,2,5]

Input: head = [1,1,1,2,3] Output: [2,3]

Constraints

The number of nodes in the list is in the range [0, 300]. -100 <= Node.val <= 100 The list is guaranteed to be sorted in ascending order.\

Java Solution

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if (head == null || head.next == null) {
            return head;
        }
        ListNode result = new ListNode(0, head);
        ListNode pre = result;
        
        while(head != null && head.next != null) {
            if(head.val == head.next.val) {
                while(head.next != null && head.val == head.next.val) {
                    head = head.next;
                }
                head = head.next;
                pre.next = head;
            } else {
                head = head.next;
                pre = pre.next;
            }
        }
        
        return result.next;
    }
}