1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstdlib>
 4 #include <cstring>
 5 #include <mutex>
 6 #include <thread>
 7 using namespace std;
 8 
 9 #define ll long long
10 
11 const int maxn=1e5+10;
12 
13 class Singleton {
14 public:
15     static Singleton* getInstance() {
16         if (instance == nullptr) {
17             lock_guard<mutex> lock(mtx);
18             if (instance == nullptr)
19                 instance = new Singleton();
20         }
21         return instance;
22     }
23 
24     void dosomething() {
25     }
26 
27     static void destoryInstance() {
28         if (instance != nullptr) {
29             delete instance;
30             instance = nullptr;
31         }
32     }
33 private:
34     Sinleton(const Singleton&) = delete;
35     Singleton& operator=(const Singleton&) = delete;
36 
37     static Singleton *instance;
38     static mutex mtx;
39 };
40 
41 void threadFunc(int id)
42 {
43     cout << "thread " + to_string(id) << endl;
44     Singleton *s = Singleton::getInstance();
45     s -> dosomething();
46 }
47 
48 Singleton * Singleton::instance = nullptr;
49 mutex Singleton::mtx;
50 
51 int main()
52 {
53     thread t1(threadFunc, 1);
54     thread t2(threadFunc, 2);
55     thread t3(threadFunc, 3);
56     t1.join();
57     t2.join();
58     t3.join();
59     Singleton::destoryInstance();
60     return 0;
61 }