实验6 C++

任务四：

Vector.hpp

#pragma once
#include <iostream> 
#include <stdexcept>

using namespace std;

template <typename T>
class Vector {
public:
	Vector(int n, int p = 0);
	Vector(const Vector<T> &v);
	~Vector();
	
	int get_size() const;
	T& at(int i);
	T& operator[](int i);
private:
	int size;
	T *a;
	
	template <typename T1>
	friend void output(const Vector<T1> &v);
};
template <typename T>
Vector<T>::Vector(int n, int p) : size{n} {
	if(n < 0)
	    throw length_error("Vector constructor: negative size");
	else {
		a = new T [n];
		for(int i = 0; i < n; i++)
		    a[i] = p; 
	}
}

template <typename T>
Vector<T>::Vector(const Vector<T> &v) {
	size = v.size;
	a = new T [size];
	for(int i = 0; i < size; i++)
	    a[i] = v.a[i];
}

template <typename T>
Vector<T>::~Vector() {
	delete [] a;
}

template <typename T>
int Vector<T>::get_size() const {return size;}

template < typename T> 
T& Vector<T>::at(int i) {
	if(i >= size || i < 0)
	    throw invalid_argument("Vector: index out of range");
	else
	    return a[i];
}

template <typename T> 
T& Vector<T>::operator[](int i) {
	if(i >= size || i < 0)
	    throw invalid_argument("Vctor: index out of range");
	else
	    return a[i];
}

template <typename T1>
void output(const Vector<T1> &v) 
{
	for(int i = 0; i < v.size - 1; i++)
	    cout << v.a[i] << ", ";
	cout << v.a[v.size - 1] << endl;
}

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：

任务五：

task5.cpp

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

using namespace std;

class Stu {
public:
	Stu() = default;
	~Stu() = default;
	
	string get_major() const {return major;}
	int get_score() const {return score;}
	
	friend ostream& operator<<(ostream &out, const Stu &s);
	friend istream& operator>>(istream &in, Stu &s);
	
private:
	string no;
	string name;
	string major;
	int score;   
};
ostream& operator<<(ostream &out, const Stu &s) {
	out << setiosflags(ios_base::left);
	out << setw(10) << s.no
	    << setw(10) << s.name
	    << setw(10) << s.major
	    << setw(10) << s.score << endl;
	return out;
}

istream& operator>>(istream &in, Stu &s) {
	in >> s.no >> s.name >> s.major >> s.score;
	return in;
}

bool cmp(const Stu &s1, const Stu &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;
}

void output(ostream &out, const vector<Stu> &v) {
	for(auto &i : v)
	    out << i ;
}

void load(const string &filename, vector<Stu> &v) {
	ifstream in(filename);
	if(!in.is_open()) {
		cout << "fail to open file to read" << endl;
		return;                   
	}
	string title_line;
	getline(in, title_line);
	
	Stu s;
	while(in >> s)
	    v.push_back(s);
	in.close();
}

void save(const string &filename, vector<Stu> &v) {
	ofstream out(filename);
	if(!out.is_open()) {
		cout << "fail to open file to write" << endl;
		return;
	}
	output(out, v);
	out.close();
}

int main() {
	vector<Stu> v;
	load("data5.txt", v);
	sort(v.begin(), v.end(), cmp);
	output(cout, v);
	save("ans5.txt", v);
}

运行结果：