83. Remove Duplicates from Sorted List

Problem:

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

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

05/01/2018 update:
A better solution can be applied to II.

public ListNode deleteDuplicates(ListNode head) {
    ListNode current = head;
    while (current != null && current.next != null) {
        if (current.next.val == current.val) {
            current.next = current.next.next;
        } else {
            current = current.next;
        }
    }
    return head;
}

Analysis:

看了II,这道题就非常简答了。

We can always move head to head.next. When encounters duplicate, use head.next = head.next.next.

Solution:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        while (head != null) {
            while (head != null && head.next != null && head.val == head.next.val) {
                head.next = head.next.next;
            }
            head = head.next;
        }
        return dummy.next;
    }
}