实验6 模板类、文件I/O和异常处理

任务4：

Vector.hpp

#pragma once

#include<iostream>
#include<stdexcept>
using namespace std;
template<typename T>
class Vector{
public:
Vector(size_t n = 0) : size_(n) {
        if (n < 0) {
            throw std::length_error("数组大小不能为负");
        }
        try {
            elements = new T[n];
        } catch (const std::bad_array_new_length&) {
            // 重新抛出更合适的异常或者进行其他处理
            throw std::length_error("数组大小不能为负");
        }
    }

    // 构造函数，指定大小并初始化为给定值
    Vector(size_t n, const T& value) : size_(n) {
        if (n < 0) {
            throw std::length_error("数组大小不能为负");
        }
        try {
            elements = new T[n];
            for (size_t i = 0; i < n; ++i) {
                elements[i] = value;
            }
        } catch (const std::bad_array_new_length&) {
            // 重新抛出更合适的异常或者进行其他处理
            throw std::length_error("数组大小不能为负");
        }
    }
    Vector(const Vector<T>& other):size_(other.size_){
        elements = new T[size_];
        for (size_t i = 0; i < size_; ++i) {
            elements[i] = other.elements[i];
        }
    }
    ~Vector(){
        delete[] elements;
    }
    
    size_t get_size() const {return size_;}
    T& at(size_t index){
        if(index>=size_){
            throw out_of_range("下标越界");
        }
        return elements[index];
    }
    
    T& operator[](size_t index){
        if(index>=size_){
            throw out_of_range("下标越界");
        }
        return elements[index];
    }
    
    friend output(const Vector<T>& v){
        for(size_t i=0;i<v.size_;++i){
            cout<<v.elements[i]<<" ";
        }
        cout<<endl;
    }
    
private:
    size_t size_;
    T *elements;
};    

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();
}

运行结果截图

任务5：

 task5.cpp

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

using std::string;
using std::ostream;
using std::istream;
using std::setw;
using std::setprecision;
using std::setiosflags;
using std::ios_base;

class People{
    private:
        string no;//学号
        string name;//姓名
        string major;//专业
        int score;//分数
         
    public:
    People()=default;
    ~People()=default;
    int get_score() const{return score;} 
    string get_string() const{return major;}
    
    friend ostream& operator<<(ostream &out, const People &c);
    friend istream& operator>>(istream &in, People &c);
};

//重载<<
ostream& operator<<(ostream &out, const People &c) {
    out << setiosflags(ios_base::left);
    out << setw(15) << c.no
        << setw(15) << c.name
        << setw(15) << c.major
        << setw(15) << c.score; 
    return out;
}

//重载>>
istream& operator>>(istream &in, People &c) {
    in >> c.no >> c.name >> c.major >> c.score;
    return in;
}

//专业按字典序排序 相同按分数排序 
bool compare_by_order(const People &p1,const People &p2) {
    if(p1.get_string()<p2.get_string())
    return true;
    
    if(p1.get_string()==p2.get_string())
    return p1.get_score()>p2.get_score();
    
    return false;
}

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

// 把vector<People>对象中的元素写到filename文件中
void save(const std::string &filename, std::vector<People> &v) {
    using std::ofstream;
    ofstream out(filename);
    if(!out.is_open()) {
    std::cout << "fail to open file to write\n";
    return;
    }
    output(out, v);
    out.close();
}

// 从文件filename读取参赛选手信息到vector<People>对象
void load(const std::string &filename, std::vector<People> &v) {
    using std::ifstream;
    ifstream in(filename);
    if(!in.is_open()) {
        std::cout << "fail to open file to read\n";
    return;
}
std::string title_line;
getline(in, title_line); // 跳过标题行
People t;
while(in >> t)
    v.push_back(t);
    in.close();
}

void test(){
    using namespace std;
    
    vector<People> v;
    
    load("data5.txt",v);//从文件加载
    sort(v.begin(),v.end(),compare_by_order);//排序
    output(cout,v);//输出到屏幕
    save("ans5.txt",v);//保存到文件 
}

int main(){
    test();
}

运行结果截图