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ACompany *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BCompany *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;
}