一、实验目的：

掌握类中静态成员的定义方法，初始化方法，使用方法；
掌握类的友元说明方法，理解友元的使用特点

二、实验内容：

1、编写程序，统计某旅馆住宿客人的总数，要求输入客人姓名，输出客人编号（按先后顺序自动生成），姓名以及总人数。

#include<iostream>
#include<stdlib.h>
#include<iomanip>
using namespace std;
struct ListPeople {
    int num;
    string name;
    struct ListPeople* next;
    ListPeople(int num, string name)
    {
        this->num = num;
        this->name = name;
    }
};
void sumpeople(ListPeople* m)//输出总人数
{
    int sum = 0;
    while (m->next != NULL)
    {
        sum++;
        m = m->next;
    }
    cout <<"总人数为：" << sum << "人" << endl;
}
int main()
{
    int num = 0;
    string name = "";
    ListPeople* head = new ListPeople(num, name);
    head->next = NULL;
    int number = 0;
    cout << "输入0查看客人总数" << endl;
    cout << "输入1客人入住" << endl;
    cout << "输入2客人退房" << endl;
    cout << "输入-1退出" << endl;
    while (number != -1)
    {
        cout << "请输入编号：";
        cin >> number;
        switch (number)
        {
        case 0://输出总人数
        {
            sumpeople(head);
            break;
        }
        case 1://客人入住
        {
            cout << "请输入入住客人姓名：";
            cin >> name;
            num++;
            ListPeople* q = new ListPeople(num, name);
            ListPeople* p = head;
            while (p->next != NULL)
                p = p->next;
            p->next = q;
            q->next = NULL;
            cout << "客人编号为：" << setw(4) << setfill('0') << q->num << "，客人姓名为：" << q->name << endl;
            sumpeople(head);
            break;
        }
        case 2://客人退房
        {
            ListPeople* m = head;
            int flag = 0;
            if (m->next == NULL)
            {
                cout << "目前没有客人入住，无法退房！" << endl;
                break;
            }
            cout << "请输入退订客人姓名：";
            cin >> name;
            while (m->next != NULL)
            {
                if (m->next->name == name)
                {
                    ListPeople* d = m->next;
                    m->next = m->next->next;
                    delete d;
                    cout << "客人退订成功" << endl;
                    sumpeople(head);
                    flag = 1;
                    break;
                }
                m = m->next;
            }
            if (flag == 0)
                cout << "未查找到该客人！" << endl;
            break;
        }           
        default:
            if (number != -1)
                cout << "请重新输入" << endl;
            else
                cout << "已退出" << endl;
        }
    }   
    return 0;
}

2、编写学生类Stu，包含学生姓名，成绩，设计一个友员函数，将学生成绩按大到小排序。

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
class Stu {
private:
    string name;
    float score;
public:
    Stu(string name, float score) : name(name), score(score) {}
    friend bool operator<(const Stu& s1, const Stu& s2);
    void print() {
        cout << "Name: " << name << ", Score: " << score << endl;
    }
};
bool operator<(const Stu& s1, const Stu& s2) {
    return s1.score > s2.score;
}
int main() {
    std::vector<Stu> students;
    // 添加学生信息
    students.push_back(Stu("Tom", 85.5));
    students.push_back(Stu("Alice", 92.0));
    students.push_back(Stu("John", 78.5));
    students.push_back(Stu("Emma", 95.0));
    // 按成绩排序
    std::sort(students.begin(), students.end());
    // 输出排序结果
    for (auto it : students) {
        it.print();
    }
    return 0;
}

1、编写整型数组类 arrow，能创建任意长度数组对象，用深复制

#include <iostream>
#include <cstring>
using namespace std;

class Array {
public:
  int* arr;
  int size;
  
  Array(int length) {
  size = length;
  arr = new int[length];
  }
  
  Array(const Array &a) {
  size = a.size;
  arr = new int[size];
  memcpy(arr, a.arr, size*sizeof(int)); 
  }
  
  ~Array() {
  delete[] arr;
  }
};

int main() {
  Array a(5);
  int n;
  int x;
  cin>>n;
  for(int i=0;i<n;i++)
    cin>>x,a.arr[i]=x;
  Array b(a);
  for(int i=0;i<n;i++)
    cout << b.arr[i] << " " ;
  
  return 0;
}

2、已知三点座标，求三角形的面积。

#include <iostream>
#include <cmath>

using namespace std;

double getTriangleArea(int x1, int y1, int x2, int y2, int x3, int y3) {
  double a = sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
  double b = sqrt((x3-x2)*(x3-x2) + (y3-y2)*(y3-y2)); 
  double c = sqrt((x1-x3)*(x1-x3) + (y1-y3)*(y1-y3));

  double s = (a + b + c) / 2;

  return sqrt(s*(s-a)*(s-b)*(s-c));
}

int main() {
  int x1 , y1 ;
  int x2 , y2 ; 
  int x3 , y3 ;
  cin>>x1>>y1;
  cin>>x2>>y2;
  cin>>x3>>y3;

  double area = getTriangleArea(x1, y1, x2, y2, x3, y3);

  cout << "Triangle area is: " << area << endl;

  return 0;
}