懒汉模式：

#include
    
     using namespace std;class Single_Lazy{public:    static Single_Lazy *getInstance()    {        if (s == nullptr)        {            s = new Single_Lazy();        }        return s;    }private:    Single_Lazy()    {}    static Single_Lazy *s;};Single_Lazy *Single_Lazy:: s = nullptr;void test1(){    Single_Lazy *s1 = Single_Lazy::getInstance();    Single_Lazy *s3 = Single_Lazy::getInstance();    Single_Lazy *s2 = Single_Lazy::getInstance();    if (s1 == s3)    {        cout << "指向同一个对象" << endl;    }    else    {        cout << "指向不是同一个对象" << endl;    }}int main(){    test1();    system("pause");}
    

懒汉模式是线程不安全的需要加锁

饿汉模式：

#include
    
     using namespace std;class Single_Hunger{public:    static Single_Hunger *getInstance()    {        return s;    }private:    Single_Hunger()    {}    static Single_Hunger *s;};Single_Hunger *Single_Hunger::s = new Single_Hunger();void test1(){    Single_Hunger *s1 = Single_Hunger::getInstance();    Single_Hunger *s2 = Single_Hunger::getInstance();    if (s1 == s2)    {        cout << "指向同一个对象" << endl;    }    else    {        cout << "指向不是同一个对象" << endl;    }}int main(){    test1();    system("pause");}