LeetCode

题目：

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.

思路：

package list;

public class RemoveDuplicatesFromSortedListII {
    
    public ListNode deleteDuplicates(ListNode head) {
        ListNode p = new ListNode(0);
        p.next = null;
        ListNode prev = p;
        
        ListNode q = head;
        while (head != null) {
            while (q.next != null && q.next.val == head.val)
                q = q.next;
            if (q == head) {
                prev.next = head;
                prev = prev.next;
            }
            
            head = q.next;
            q = head;
        }
        
        prev.next = null;
        return p.next;
    }
    
    public static void main(String[] args) {
        ListNode a1 = new ListNode(1);
        ListNode a2 = new ListNode(2);
        ListNode a3 = new ListNode(2);
        ListNode a4 = new ListNode(3);
        ListNode a5 = new ListNode(4);
        a1.next = a2;
        a2.next = a3;
        a3.next = a4;
        a4.next = a5;
        a5.next = null;
        RemoveDuplicatesFromSortedListII r = new RemoveDuplicatesFromSortedListII();
        ListNode head = r.deleteDuplicates(a1);
        while (head != null) {
            System.out.println(head.val);
            head = head.next;
        }
    }

}