# Leetcode 83. Remove Duplicates from Sorted List
###### tags: `Leetcode`

題目
Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.

Example 1:

Input: head = [1,1,2]
Output: [1,2]
Example 2:

Input: head = [1,1,2,3,3]
Output: [1,2,3]

解法:
1.從203.稍微修改一下就可以了
2.記得preval要更新(如果當下那個不是重複的話)

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */


struct ListNode* deleteDuplicates(struct ListNode* head){
    if(head == NULL)
        return NULL;
    if(head->next == NULL)
        return head;
    int preval = head->val;
    
    struct ListNode* pre = head;
    struct ListNode* cur = head->next;
    while(cur != NULL)
    {
        if(cur->val == preval)
            pre->next = cur->next;
        else
        {
            pre = cur;
            preval = cur->val;
        }
            
        cur = cur->next;
    }
    return head;
}