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.

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这是个没有头结点的链表，我们只要将重复的删掉即可（因为链表是排好序的，我们只要判断后者的值是否等于前者，如果等于则删掉）

 

/**
 * 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)return head;
        ListNode *pre = head, *current = pre->next;
        while (current)
        {
            if (current->val == pre->val)
            {
                pre->next = current->next;
                free(current);
                current = pre->next;
            }
            else
            {
                current = current->next;
                pre = pre->next;
            }
        } 
        return head;
    }
};