vector_int.hpp:

#ifndef VECTOR_INT_H
#define VECTOR_INT_H
#include<iostream>
#include<cassert>

using namespace std;

class vector_int {
public:
    vector_int(int n) :size{ n } {
        cout << "Default constructor called." << endl;
        p = new int[size];
        for (int i = 0; i < size; i++)
            p[i] = 0;
    }
    vector_int(int n, int m) :size{ n }, value{ m }{
        cout << "Constructor called." << endl;
        p = new int[size];
        for (int i = 0; i < size; i++)
            p[i] = value;
    }
    vector_int(const vector_int& x) :size{ x.size } {
        cout << "Copy constructor called." << endl;
        p = new int[size];
        for (int i = 0; i < size; i++)
            p[i] = x.p[i];
    }
    ~vector_int()
    {
        cout << "Destructor called" << endl;
        delete[] p;
    }
    int& at(int i) {
        assert(i >= 0 && i < size);
        return p[i];
    }
    void show() const {
        for (int i = 0; i < size; i++)
            cout << p[i] << " ";
        cout << "\b\n";
    }
private:
    int size, value;
    int* p;
};
#endif // !VECTOR_INT_H

task4.cpp:

#include<iostream>
#include"vector_int.hpp"
using namespace std;
int main() {
    int n;
    cin >> n;
    vector_int x1(n);
    x1.show();
    vector_int x2(n, 6);
    x2.show();
    vector_int y(x2);
    y.at(0) = 999;
    y.show();
}

结果截图：

Matrix.hpp:

#ifndef MATRIX_HPP
#define MATRIX_HPP
#include <iostream>
#include <cassert>

using namespace std;

class Matrix {
public:
    Matrix(int n);
    Matrix(int n, int m);
    Matrix(const Matrix& x);
    ~Matrix();
    void set(const double* pvalue);
    void set(int i, int j, int value);
    double& at(int i, int j);
    double at(int i, int j)const;
    int get_lines()const;
    int get_cols()const;
    void print()const;
private:
    int lines;
    int cols;
    double* p;
};

Matrix::Matrix(int n) :lines{ n }, cols{ n }{
    p = new double[n * n];
}

Matrix::Matrix(int n,int m ): lines{ n }, cols{ m }{
    p = new double[n * m];
}

Matrix::Matrix(const Matrix& X) : lines{ X.lines }, cols{ X.cols }{
    p = new double[lines * cols];
    for (int i = 0; i < lines * cols; i++)
        p[i] = X.p[i];
}

Matrix::~Matrix() {
    delete[] p;
}

void Matrix::set(const double* pvalue) {
    for (int i = 0; i < lines * cols; i++) {
        p[i] = pvalue[i];
    }
}

void Matrix::set(int i, int j, int value)
{
    assert(i >= 0 && i < lines&& j >= 0 && j < cols);
    p[i * cols + j] = value;
}

double& Matrix::at(int i, int j) {
    assert(i >= 0 && i < lines&& j >= 0 && j < cols);
    return p[i * cols + j];
}

double Matrix::at(int i, int j)const {
    assert(i >= 0 && i < lines&& j >= 0 && j < cols);
    return p[i * cols + j];
}

int Matrix::get_lines() const {
    return lines;
}

int Matrix::get_cols() const {
    return cols;
}

void Matrix::print()const {
    for (int i = 0; i < lines; i++) {
        for (int j = 0; j < cols; j++)
            cout << p[i * cols + j] << " ";
        cout << "\b\n";
    }
}
#endif // !MATRIX_HPP

task5.cpp:

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

int main()
{
    using namespace std;

    double x[] = { 10, 20, 30, 40, 50, 60 };

    Matrix m1(3, 2);    // 创建一个3×2的矩阵
    m1.set(x);          // 用一维数组x的值按行为矩阵m1赋值
    m1.print();         // 打印矩阵m1的值
    cout << "the first line is: " << endl;
    cout << m1.at(0, 0) << " " << m1.at(0, 1) << endl;
    cout << endl;

    Matrix m2(2, 3);
    m2.set(x);
    m2.print();
    cout << "the first line is: " << endl;
    cout << m2.at(0, 0) << " " << m2.at(0, 1) << " " << m2.at(0, 2) << endl;
    cout << endl;

    Matrix m3(m2);
    m3.set(0, 0, 666);
    m3.print();
}

结果截图：