添加设计模式及例子，包括：单例、抽象工厂、适配器、桥接、观察者模式

DesignPattern/SingletonPattern/README.md

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+# 单例模式
+
+```cpp
+// 懒汉式单例模式
+class Singleton
+{
+private:
+	Singleton() { }
+	static Singleton * pInstance;
+public:
+	static Singleton * GetInstance()
+	{
+		if (pInstance == nullptr)
+			pInstance = new Singleton();
+		return pInstance;
+	}
+};
+
+// 线程安全的单例模式
+class Singleton
+{
+private:
+	Singleton() { }
+	~Singleton() { }
+	Singleton(const Singleton &);
+	Singleton & operator = (const Singleton &);
+public:
+	static Singleton & GetInstance()
+	{
+		static Singleton instance;
+		return instance;
+	}
+};
+```

DesignPattern/SingletonPattern/Singleton.cpp

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+//
+// Created by xiemenghui on 2018/7/20.
+//
+
+#include <iostream>
+#include "Singleton.h"
+
+void Singleton::DoSomething()
+{
+    std::cout << "Singleton do something\n";
+}

DesignPattern/SingletonPattern/Singleton.h

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+//
+// Created by xiemenghui on 2018/7/20.
+//
+
+#ifndef DESIGNPATTERN_SINGLETON_H
+#define DESIGNPATTERN_SINGLETON_H
+
+// 单例模式
+class Singleton {
+private:
+    Singleton(){}
+    ~Singleton(){}
+    Singleton(const Singleton &);
+    Singleton & operator= (const Singleton &);
+
+public:
+    static Singleton & GetInstance()
+    {
+        static Singleton instance;
+        return instance;
+    }
+    void DoSomething();
+};
+
+#endif //DESIGNPATTERN_SINGLETON_H

DesignPattern/SingletonPattern/SingletonMain.h

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+//
+// Created by xiemenghui on 2018/7/20.
+//
+
+#ifndef DESIGNPATTERN_SINGLETONMAIN_H
+#define DESIGNPATTERN_SINGLETONMAIN_H
+
+#include "Singleton.h"
+
+void SingletonMain()
+{
+    Singleton::GetInstance().DoSomething();
+}
+
+#endif //DESIGNPATTERN_SINGLETONMAIN_H