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

deleteDuplicates.java

/**
 * 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.
    
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if (head == null) return null;
        
        ListNode cur = head;
        ListNode ahead;
        
        while(cur.next != null) {
            ahead = cur.next;
            if(ahead.val == cur.val) {
                ahead = ahead.next;
                cur.next = ahead;
            } else {
                cur = ahead;
            }
        }
        
        return head;
    }
}