380. 常数时间插入、删除和获取随机元素 

 1 class RandomizedSet 
 2 {
 3     unordered_map<int,int> hash;
 4     vector<int> nums;
 5 public:
 6     /** Initialize your data structure here. */
 7     RandomizedSet() 
 8     {
 9 
10     }
11     
12     /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
13     bool insert(int val) 
14     {
15         if(hash.count(val) > 0) return false;
16         else
17         {
18             nums.push_back(val);
19             hash.insert({val,nums.size() - 1});
20             return true;
21         }
22     }
23     
24     /** Removes a value from the set. Returns true if the set contained the specified element. */
25     bool remove(int val) 
26     {
27         if(hash.count(val) == 0) return false;
28         else
29         {
30             int index = hash[val];
31 
32             hash[nums.back()] = hash[val];//nums最后一个值的哈希值进行更新
33             
34             swap(nums[index],nums[nums.size() - 1]);//对最后一个值进行删除
35             nums.pop_back();
36 
37             hash.erase(val);
38 
39             return true;
40         }
41     }
42     
43     /** Get a random element from the set. */
44     int getRandom() 
45     {
46         return nums[rand() % (int)nums.size()];
47     }
48 };
49 
50 /**
51  * Your RandomizedSet object will be instantiated and called as such:
52  * RandomizedSet* obj = new RandomizedSet();
53  * bool param_1 = obj->insert(val);
54  * bool param_2 = obj->remove(val);
55  * int param_3 = obj->getRandom();
56  */

 

posted @ 2020-04-27 11:22  Jinxiaobo0509  阅读(110)  评论(0)    收藏  举报