任务5 源代码：

info.hpp

#ifndef INFO_HPP
#define INFO_HPP

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

class Info
{
public:
    Info(const string nickname0, const string contact0, const string city0, int n0);
    void print()const;
private:
    string nickname;
    string contact;
    string city;
    int n;
};

Info::Info(const string nickname0="", const string contact0 = "", const string city0 = "", int n0=0):nickname{nickname0},contact{contact0},city{city0},n{n0}{}
void Info::print()const
{
    cout.width(10);
    cout << setiosflags(ios::left) << "称呼：";
    cout << this->nickname << endl;
    cout.width(10);
    cout << setiosflags(ios::left) << "联系方式：";
    cout << this->contact << endl;
    cout.width(10);
    cout << setiosflags(ios::left) << "所在城市：";
    cout << this->city<< endl;
    cout.width(10);
    cout << setiosflags(ios::left) << "预定人数：";
    cout << this->n << endl;
}

#endif

task5.cpp

#include"Info.hpp"
#include<iostream>
#include<vector>
#include<string>

int main()
{
    using namespace std;
    vector<Info>audience_info_list;
    const int capacity = 100;
    string nickname, contact, city;
    int n,total = 0;
    char choice;

    cout << "录入信息：" << endl<<endl;
    cout << "称呼/昵称，联系方式（邮箱/手机号），所在城市，预定参加人数" << endl;
    while (cin >> nickname)
    {
        cin >> contact;
        cin >> city;
        cin >> n;
        if (n + total <= capacity)
        {
            Info audience_information(nickname, contact, city, n);
            audience_info_list.push_back(audience_information);
            total += n;
        }
        else
        {
            cout << "对不起，只剩" << capacity - total << "个位置." << endl;
            cout << "1.输入u，更新(update)预定信息" << endl;
            cout << "2.输入q，退出预定" << endl;
            cout << "你的选择：";
            cin >> choice;
            if (choice == 'u')
            {
                cout << "请重新输入预定参加人数：" << endl;
                cin >> n;
                Info audience_information(nickname, contact, city, n);
                audience_info_list.push_back(audience_information);
                total += n;
                cout << "继续录入信息：" << endl << endl;
                cout << "称呼/昵称，联系方式（邮箱/手机号），所在城市，预定参加人数" << endl;
            }
            else 
                break;
        }
        
    }
    cout << "截至目前，一共有" << total << "位听众预定参加。预定听众信息如下："<<endl;
    for (auto Info : audience_info_list)
    {
        Info.print();
        cout << endl;
    }
    return 0;
}

 任务6 源代码：

textcoder.hpp

#ifndef TEXTCORDER_HPP
#define TEXTCORDER_HPP

#include<iostream>
#include<string>
using namespace std;
class TextCoder
{
public:
    TextCoder(string text0 = "") : text{ text0 } {  }
    ~TextCoder() = default;
    string encoder();
    string decoder();
private:
    string text;
};

string TextCoder::encoder()
{
    string res;
    for (int i = 0; i < this->text.size(); i++)
    {
        if (text[i] >= 'a' && text[i] <= 'u')
            res.push_back(text[i] += 5);
        else if (text[i] >= 'v' && text[i] <= 'z')
            res.push_back(text[i] -= 21);
        else if (text[i] >= 'A' && text[i] <= 'U')
            res.push_back(text[i] += 5);
        else if (text[i] >= 'V' && text[i] <= 'Z')
            res.push_back(text[i] -= 21);
    }
    return res;
}

string TextCoder::decoder()
{
    string res;
    for (int i = 0; i < this->text.size(); i++)
    {
        if (text[i] >= 'f' && text[i] <= 'z')
            res.push_back(text[i] -= 5);
        else if (text[i] >= 'a' && text[i] <= 'e')
            res.push_back(text[i] += 21);
        else if (text[i] >= 'F' && text[i] <= 'Z')
            res.push_back(text[i] -= 5);
        else if (text[i] >= 'A' && text[i] <= 'E')
            res.push_back(text[i] += 21);
    }
    return res;
}

#endif

task6.cpp

#include "textcoder.hpp" 
#include <iostream> 
#include <string>
int main()
{
    using namespace std;
    string text, encoded_text, decoded_text;
    cout << "输入英文文本: "; 
    while (getline(cin, text))
    {
        encoded_text = TextCoder(text).encoder(); // 这里使用的是临时无名对象
        cout << "加密后英文文本:\t" << encoded_text << endl;
        decoded_text = TextCoder(encoded_text).decoder(); // 这里使用的是临时无名对象
        cout << "解密后英文文本:\t" << decoded_text << endl; cout << "\n输入英文文本: ";
    }
}