（LeetCode 83）Remove Duplicates from Sorted Lists

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.

题目要求：

给一有序链表，删除重复的结点，使得每个元素只出现一次。

解题思路：

1、从头到尾遍历链表，如果前后两个结点相同，则将第一个结点指向它的下下结点，并删除它的下个结点。

2、递归思想。

代码：

/**
 * 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) {
        ListNode *lst=head;
        ListNode *del;
        while(lst && lst->next){
            if(lst->val==lst->next->val){
                del=lst->next;
                lst->next=lst->next->next;
                delete(del);
            }
            else
                lst=lst->next;
        }
        return head;
    }
};

/**
 * 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;
        if(head->val==head->next->val)
            head=deleteDuplicates(head->next);
        else
            head->next=deleteDuplicates(head->next);
        return head;
    }
};