实验6 模板类、文件I\O和异常处理

任务4

源码：

#pragma once

#include <iostream>
#include <stdexcept>

using namespace std;

// 模板类声明
template<typename T>
class Vector {
public:
    Vector(int n): size{n} {
        if(n < 0) 
            throw length_error("Vector constructor: negtive size");
        ptr = new T [size];
    }
    
    Vector(int n, T value): size{n} {
        if(n < 0) 
            throw length_error("Vector constructor: negtive size");
        ptr = new T[size];
        for(int i = 0; i < size; i++)
            ptr[i] = value;
    }

    Vector(const Vector<T> &v): size{v.size}, ptr{new T[size]} {
        for(int i = 0; i < size; i++)
            ptr[i] = v.ptr[i];        
    }
    
    ~Vector() {
        delete [] ptr;
    }

    int get_size() const {
        return size;
    }

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

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

template<typename T>
void output(const Vector<T> &v) {
    for(int i = 0; i < v.get_size(); i++)
        cout << v.at(i) << ", ";
    cout << "\b\b \n";
}

#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();
}

 

运行测试截图：

 

 

任务5

源码：

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

using std::string;
using std::vector;
using std::ostream;
using std::istream;
using std::cout;
using std::endl;
using std::setw;
using std::setprecision;
using std::setiosflags;
using std::ios_base;


class Student {
public:
    Student() {}
    ~Student() {}

    string get_major() const { return major; }
    int get_score() const { return score; }

    friend ostream& operator<<(ostream &out, const Student &s);
    friend istream& operator>>(istream &in, Student &s);

private:
    string no;          // 学号
    string name;        // 姓名
    string major;       // 专业
    int score;            // 分数 
};

// 友元函数实现
// 重载流插入运算符<<
ostream& operator<<(ostream &out, const Student &s) {
    out << setiosflags(ios_base::left);
    out << setw(15) << s.no
        << setw(15) << s.name
        << setw(15) << s.major
        << setw(5) << s.score;
 
    return out;
}

// 重载流提取运算符>>
istream& operator>>(istream &in, Student &s) {
    in >> s.no >> s.name >> s.major >> s.score;

    return in;
}


// 排序函数
bool compare_by_major(const Student &s1, const Student &s2) {
    if(s1.get_major() < s2.get_major())
        return true;
    
    if(s1.get_major() == s2.get_major())
        return s1.get_score() > s2.get_score();
    
    return false;
}

// 把vector<Student>对象中的元素插入到输出流out
void output(ostream &out, const vector<Student> &v) {
    for(auto &i: v)
        out << i << endl;
}


// 把vector<Student>对象中的元素写到filename文件中
void save(const string &filename, vector<Student> &v) {
    using std::ofstream;

    ofstream out(filename);
    if(!out.is_open()) {
        cout << "fail to open file to write\n";
        return;
    }

    output(out, v);
    out.close();
}

// 从文件filename读取学生信息到vector<Student>对象
void load(const string &filename, vector<Student> &v) {
    using std::ifstream;

    ifstream in(filename);
    if(!in.is_open()) {
        cout << "fail to open file to read\n";
        return;
    }

    string title_line;
    getline(in, title_line);     // 跳过标题行

    Student t;
    while(in >> t) 
        v.push_back(t);

    in.close();
}


void test() {
    using namespace std;

    vector<Student> v;

    load("data5.txt", v);   // 从文件加载选手信息到对象v
    sort(v.begin(), v.end(), compare_by_major);  // 按解题情况排序
    output(cout, v);    // 输出对象v中信息到屏幕
    save("ans5.txt", v); // 把对象v中选手信息保存到文件
}

int main() {
    test();
}

 

运行测试截图：

 

总结：

文件读写过程中可能由于文本文档格式不同，出现乱码现象，修改格式即可