题解 | 删除有序链表中重复的元素-II

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    ListNode* deleteDuplicates(ListNode* head) {
        // write code here
        int a[2010] = {};
        while(head != nullptr) 
        {
            if(head -> val < 0)
                head -> val = - (head -> val) + 1000;
            a[head -> val] ++;
            head = head -> next;
        }
        ListNode* phead = new ListNode(-1);
        ListNode* cur = phead;
        for(int i = 2010; i >= 1001; i --) 
        {
            if(a[i] != 0 && a[i] == 1) 
            {
                ListNode* p = new ListNode(-(i - 1000));
                cur -> next = p;
                cur = cur -> next;
            }
        }
        for(int i = 0; i <= 1000; i ++) 
        {
            if(a[i] != 0 && a[i] == 1) 
            {
                ListNode* p = new ListNode(i);
                cur -> next = p;
                cur = cur -> next;
            }
        }
        return phead -> next;
    }
};