82. Remove Duplicates from Sorted List II - jiejackyzhang/leetcode-note GitHub Wiki

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

For example, Given 1->2->3->3->4->4->5, return 1->2->5. Given 1->1->1->2->3, return 2->3.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode prev = dummy;
        ListNode cur = head;
        while(cur != null) {
            while(cur.next != null && cur.val == cur.next.val) cur = cur.next;
            if(prev.next == cur) {
                prev = prev.next; // no duplicates
            } else {
                prev.next = cur.next; // remove duplicates
            }
            cur = cur.next;
        }
        return dummy.next;
    }
}