LeetCode 83 Remove Duplicates from Sorted List

相同的时候，prev指针不动，cur.next = cur.next.next

不相同的时候， prev跟cur指针同时更新。

/**
 * class ListNode {
 *   public int value;
 *   public ListNode next;
 *   public ListNode(int value) {
 *     this.value = value;
 *     next = null;
 *   }
 * }
 */
public class Solution {
  public ListNode removeDup(ListNode head) {
    // Write your solution here
    if (head == null) {
         return head; 
    }
    ListNode prev = head, cur = head;
    while (cur.next != null) {
        if (cur.value == cur.next.value) {
          cur.next = cur.next.next; 
      } else {
        prev = cur;
           cur = cur.next;
      }
    }
    return head;
  }
}