LeetCode题解：Remove Duplicates from Sorted List II

Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving onlydistinct numbers from the original list.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

思路：

这次要求只保留出现一次的元素。依然是一次遍历链表，用一个临时链表挂上第一次出现的元素。如果之后发现了重复，就把这个元素去掉，挂上新的元素。这里为了简单，就用了一个vector。

题解：

/** * 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) {        // empty list        if (head == nullptr)            return nullptr;        vector<ListNode*> unique;                unique.push_back(head);        ListNode* iter = head->next;        bool dup = false;                while(iter != nullptr)        {            if (iter->val == unique.back()->val)            {                dup = true;                ListNode* tmp = iter;                iter = iter->next;                delete tmp;            }            else            {                if (dup)                {                    delete unique.back();                    unique.pop_back();                }                dup = false;                unique.push_back(iter);                iter = iter->next;            }        }                if (dup)            unique.pop_back();                if (unique.empty())            return nullptr;        for(int  i = 0; i < unique.size() - 1; ++i)            unique[i]->next = unique[i + 1];                unique.back()->next = nullptr;        return unique.front();    }};