Remove Duplicates from Sorted List

slowrunner and fastrunner trick

/**
 * 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) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        ListNode fakehead = new ListNode(0);
        fakehead.next = head;
        ListNode runner = fakehead;
        while(runner.next != null){
            if(runner.val == runner.next.val && runner != fakehead)
                runner.next = runner.next.next;
            else
                runner = runner.next;
        }
        return fakehead.next;
    }
}