[LeetCode] Problem 82 - Remove Duplicates from Sorted List II

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

Example

No.1

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

Output: 1->2->5

No.2

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

Output: 2->3

Code

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public class ListNode {
    int val;
    ListNode next = null;
    ListNode(int x) { val = x; }
}
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public ListNode deleteDuplicates(ListNode head) {
    ListNode dummy = new ListNode(0);
    dummy.next = head;
    ListNode prev = dummy;
    ListNode current = head;

    while (current != null && current.next != null) {
        if (current.val == current.next.val) {
            while (current.next != null && current.next.val == prev.next.val)
                current = current.next;

            current = current.next;
            prev.next = current;
        }
        else {
            prev = current;
            current = current.next;
        }
    }

    return dummy.next;
}