题目描述

法一）直接删除法

class Solution{
public:
	ListNode* deleteDuplicates(ListNode* head) {
        if(head==NULL) return NULL;
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        ListNode* cur = dummy;
        while(cur->next!=NULL && cur->next->next!=NULL){
        	if(cur->next->val == cur->next->next->val){
        		int temp = cur->next->val;
        		while(cur->next!=NULL && cur->next->val == temp){
        			cur->next = cur->next->next;
				} 
			}
			else {
				cur = cur->next;
			}
		}
		return dummy->next;
    }
};

法二）哈希表

class Solution{
public:
	ListNode* deleteDuplicates(ListNode* head) {
		if(head==NULL) return NULL;
		unordered_map<int, int>	mp;
		ListNode* cur = head;
		while(cur!=NULL){
			mp[cur->val]++;
			cur = cur->next;
		}
		ListNode* dummy = new ListNode(0);
		dummy->next = head;
		cur = dummy;
		while(cur->next){
			if(mp[cur->next->val]!=1){
				cur->next = cur->next->next;
			}
			else{
				cur = cur->next;
			}
		}
		return dummy->next;
	}
};