实验6 模板类、文件I/O和异常处理

task4

Vector.hpp

#pragma once

#include <iostream>
#include <stdexcept>

using std::cout; 
template <typename T>

class Vector {
public:
    Vector(int n) : size(n) {
        if (size < 0) {
            throw std::length_error("Vector constructor: negative size");
        }
    
        ptr = new T[size];
    }

    Vector(int n, T value) : size(n) {
    if (n < 0) {
        throw std::length_error("Vector constructor: negative size");
    }
    
    ptr = new T[size];
    for (int i = 0; i < size; ++i) {
        ptr[i] = value;
    }
    }
    
    Vector(const Vector<T>& vi) : size(vi.size),ptr{new int[size]} {
        for (int i = 0; i < size; ++i) {
            ptr[i] = vi.ptr[i];
        }
    }
    ~Vector() {
        delete[] ptr;
    }

    int get_size() const {
        return size;
    }

    T& at(int index) const {
        if (index < 0 || index >= size) {
            throw std::out_of_range("Vector::at(): index out of this->size");
        }
        return ptr[index];
    }
    
    T& at(int index) {
        return static_cast<const Vector*>(this)->at(index);
    }

    T& operator[](int index) const {
        if (index < 0||index >= size) {
            throw std::out_of_range("Vector::operator[]():index out of this->size");
        }
        return ptr[index];
    }
    
    T& operator[](int index) {
        return static_cast<const Vector*>(this)->operator[](index);
    }

    friend std::ostream& operator<<(std::ostream& out, const Vector<T>& v) {
        for (int i = 0; i < v.size; ++i) {
            out << v.ptr[i];
            if (i < v.size - 1) {
                out << ",";
            }
        }
        return out;
    }
    
    
    friend void output(const Vector<T>& v) {
        std::cout << v << std::endl;
    }

private:
    T* ptr;
    int size;
};

task4.cpp

#include <iostream>
#include "Vector.hpp"

void test1() {
    using namespace std;

    int n;
    cout << "Enter n: ";
    cin >> n;
    
    Vector<double> x1(n);
    for(auto i = 0; i < n; ++i)
        x1.at(i) = i * 0.7;

    cout << "x1: "; output(x1);

    Vector<int> x2(n, 42);
    const Vector<int> x3(x2);

    cout << "x2: "; output(x2);
    cout << "x3: "; output(x3);

    x2.at(0) = 77;
    x2.at(1) = 777;
    cout << "x2: "; output(x2);
    cout << "x3: "; output(x3);
}

void test2() {
    using namespace std;

    int n, index;
    while(cout << "Enter n and index: ", cin >> n >> index) {
        try {
            Vector<int> v(n, n);
            v.at(index) = -999;
            cout << "v: "; output(v);
        }
        catch (const exception &e) {
            cout << e.what() << endl;
        }
    }
}

int main() {
    cout << "测试1: 模板类接口测试\n";
    test1();

    cout << "\n测试2: 模板类异常处理测试\n";
    test2();
}

运行结果：

 

task5

task5.cpp

#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <algorithm>
#include <string>

// 学生成绩结构体
struct Student {
    std::string id;
    std::string name;
    std::string major;
    int score;
};

// 比较函数，用于按照专业字典序排序，专业内分数降序排序
bool compareStudents(const Student& s1, const Student& s2) {
    if (s1.major < s2.major) {
        return true;
    } else if (s1.major == s2.major) {
        return s1.score > s2.score;
    }
    return false;
}

// 从文件读取学生成绩信息到vector
void loadData(const std::string& filename, std::vector<Student>& students) {
    std::ifstream inFile(filename);
    if (!inFile) {
        std::cerr << "无法打开文件: " << filename << std::endl;
        return;
    }

    std::string line;
    // 跳过标题行
    std::getline(inFile, line);

    while (std::getline(inFile, line)) {
        std::istringstream iss(line);
        Student student;
        iss >> student.id >> student.name >> student.major >> student.score;
        students.push_back(student);
    }

    inFile.close();
}

// 将学生成绩信息保存到文件
void saveData(const std::string& filename, const std::vector<Student>& students) {
    std::ofstream outFile(filename);
    if (!outFile) {
        std::cerr << "无法打开文件: " << filename << std::endl;
        return;
    }

    // 写入标题行
    outFile << "学号\t姓名\t专业\t分数\n";

    for (const auto& student : students) {
        outFile << student.id << "\t" << student.name << "\t" << student.major << "\t" << student.score << "\n";
    }

    outFile.close();
}

// 输出学生成绩信息到屏幕
void printData(const std::vector<Student>& students) {
    // 输出标题行
    std::cout << "学号\t姓名\t专业\t分数\n";

    for (const auto& student : students) {
        std::cout << student.id << "\t" << student.name << "\t" << student.major << "\t" << student.score << "\n";
    }
}

int main() {
    std::vector<Student> students;
    loadData("data5.txt", students);

    std::sort(students.begin(), students.end(), compareStudents);

    printData(students);

    saveData("ans5.txt", students);

    return 0;
}

运行结果：