LeetCode Remove Duplicates from Sorted List

Description

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.

The original problem is here.

The original code is here.

My Solution

I solve this problem in C++, as below:

/*
*Remove Duplicates from Sorted List 
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/

/**
 * 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 *ptr_all = head->next;
        ListNode *ptr_use = head;
        while(ptr_all != NULL){
            if(ptr_all->val != ptr_use->val){
                ptr_use->next = ptr_all;
                ptr_use = ptr_use->next;
            }
            ptr_all = ptr_all->next;
        }
        ptr_use->next = NULL;
        return head;
    }
};

Note

Firstly, we need judge whether the list is null or only has one elemet or not.
To solve the problem, I use two pointers ptr_all and ptr_use. Then, traverse the list use ptr_all, add the unqiue number to ptr_use.