将对象组合成树形结构以表示“部分-整体”的层次结构。组合使得用户对单个对象和组合对象的使用具有一致性。注意两个字“树形”。这种树形结构在现实生活中随处可见，比如一个集团公司，它有一个母公司，下设很多家子公司。不管是母公司还是子公司，都有各自直属的财务部、人力资源部、销售部等。对于母公司来说，不论是子公司，还是直属的财务部、人力资源部，都是它的部门。整个公司的部门拓扑图就是一个树形结构。

#include<iostream>
#include<string>
#include<list>
using namespace std;

class Company
{
public:
	Company(string name) { m_name = name; }
	virtual ~Company() {}
	virtual void Add(Company *pCom) {}
	virtual void Show(int depth) {}
protected:
	string m_name;
};
//具体公司
class ConcreteCompany : public Company
{
public:
	ConcreteCompany(string name) : Company(name) {}
	virtual ~ConcreteCompany() {}
	void Add(Company *pCom) { m_listCompany.push_back(pCom); } //位于树的中间，可以增加子树
	void Show(int depth)
	{
		for (int i = 0; i < depth; i++)
			cout << "-";
		cout << m_name << endl;
		list<Company *>::iterator iter = m_listCompany.begin();
		for (; iter != m_listCompany.end(); iter++) //显示下层结点
			(*iter)->Show(depth + 2);
	}
private:
	list<Company *> m_listCompany;
};
//具体的部门，财务部
class FinanceDepartment : public Company
{
public:
	FinanceDepartment(string name) :Company(name) {}
	virtual ~FinanceDepartment() {}
	virtual void Show(int depth) //只需显示，无限添加函数，因为已是叶结点
	{
		for (int i = 0; i < depth; i++)
			cout << "-";
		cout << m_name << endl;
	}
};
//具体的部门，人力资源部
class HRDepartment :public Company
{
public:
	HRDepartment(string name) :Company(name) {}
	virtual ~HRDepartment() {}
	virtual void Show(int depth) //只需显示，无限添加函数，因为已是叶结点
	{
		for (int i = 0; i < depth; i++)
			cout << "-";
		cout << m_name << endl;
	}
};


int main()
{
	Company *root = new ConcreteCompany("总公司");
	Company *leaf1 = new FinanceDepartment("财务部");
	Company *leaf2 = new HRDepartment("人力资源部");
	root->Add(leaf1);
	root->Add(leaf2);

	//分公司A
	Company *mid1 = new ConcreteCompany("分公司A");
	Company *leaf3 = new FinanceDepartment("财务部");
	Company *leaf4 = new HRDepartment("人力资源部");
	mid1->Add(leaf3);
	mid1->Add(leaf4);
	root->Add(mid1);
	//分公司B
	Company *mid2 = new ConcreteCompany("分公司B");
	FinanceDepartment *leaf5 = new FinanceDepartment("财务部");
	HRDepartment *leaf6 = new HRDepartment("人力资源部");
	mid2->Add(leaf5);
	mid2->Add(leaf6);
	root->Add(mid2);
	root->Show(0);

	delete leaf1; delete leaf2;
	delete leaf3; delete leaf4;
	delete leaf5; delete leaf6;
	delete mid1; delete mid2;
	delete root;

	getchar();
	return 0;
}