How to realize the lazy mode and hungry man model of C++ singleton model

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Lazy man mode

The lazy pattern is not instantiated until the first time the class instance is used, but the object of this class does not exist until the getInstance function is called. The slacker itself is not thread-safe.

# include using namespace std;class Singelton {private: Singelton () {m_count + +; printf ("Singelton begin\ n"); Sleep (1000); / / add sleep to magnify the effect printf ("Singelton end\ n");} static Singelton * single;// defines a unique pointer to the instance and is private public: static Singelton * GetSingelton () / / define a public function that can get the unique instance static void print (); static int mcount;}; / / initialize the unique pointer to the instance to nullptrSingelton * Singelton::single = nullptr;int Singelton::m_count = 0 single Singelton * Singelton::GetSingelton () {if (single = = nullptr) {/ / determine whether it is the first time to use single = new Singelton;} return single } void Singelton::print () {cout