leetcode 83. Remove Duplicates from Sorted List

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.

  

可以用一个指针，也可以用两个指针来完成

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

 

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