1. Description

Given a sorted linked list, delete all duplicates such that each element appear only once.

2. Example

Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

3. Code

public class LeetCode0083 {

    class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }

    public ListNode deleteDuplicates(ListNode head) {
        ListNode dummy = new ListNode(Integer.MIN_VALUE);
        dummy.next = head;
        ListNode p = head;
        ListNode pre = dummy;
        while (p != null) {
            if (p.val == pre.val) {
                p = p.next;
            } else {
                pre.next = p;
                pre = p;
                p = p.next;
            }
        }
        pre.next = null;
        return dummy.next;
    }
}