Leetcode 83-remove duplicates from Sorted List (c + + Java Python)

Title: http://oj.leetcode.com/problems/remove-duplicates-from-sorted-list/

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

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

Title translation:

Given an ordered list, delete all duplicate elements so that each element appears only once.
For example
Given 1->1->2, returns 1->2.
Given 1->1->2->3->3, returns 1->2->3.
Analysis:
Each element is retained only once, and multiple duplicate elements are deleted once.
C + + implementation:

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode (int x): Val (x), Next (NULL) {}
 *};
 * *
class Solution {public
:
    listnode *deleteduplicates (ListNode *head) {
    	if (head = = NULL | | head- >next = = NULL) {return head
    		;
    	}

    	ListNode *pre = head;
    	ListNode *cur = head->next;

    	while (cur!= NULL)
    	{
    		if (cur->val!= pre->val)
    		{
    			pre = cur;
    			cur = cur->next;
    			Continue;
    		}

    		while (Cur->next!= NULL && cur->next->val = = pre->val)
    		{
    			cur = cur->next;
    		}

    		Pre->next = cur->next;
    		cur = pre->next;
    	}

    	return head;
    }
;

Java implementation:

/**
 * 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) {
        if ( Head = = NULL | | Head.next = = null) {return head
			;
		}

		ListNode pre = head;
		ListNode cur = head.next;

		while (cur!= null) {
			if (cur.val!= pre.val) {
				pre = cur;
				cur = cur.next;
				Continue;
			}

			while (Cur.next!= null && cur.next.val = = pre.val) {
				cur = cur.next;
			}

			Pre.next = Cur.next;
			cur = pre.next;
		}

		return head;
    }

Python implementations:

# Definition for singly-linked list.
# class ListNode:
#     def __init__ (self, x):
#         self.val = x
#         Self.next = None

class Solution :
    # @param head, a listnode
    # @return a listnode
    def deleteduplicates (self, head):
        if head = = None or He Ad.next = none: Return head
        
        pre =
        cur = head.next while
        
        cur!= none:
            if Cur.val!=:
                pre = cur
                cur = cur.next
                continue while
            
            Cur.next!= None and Cur.next.val = = Pre.val:
                cur = cur. Next
            
            pre.next = cur.next
            cur = pre.next return head
        
        

Thank you for reading and welcome comments.