C++实验3

#ifndef VECTOR_HPP
#define VECTOR_HPP

#include<iostream>
#include<cassert>
using namespace std;

class vector_int {
public:
    //vector_int();
    vector_int(int n);
    vector_int(int n, int vaule);
    vector_int(const vector_int& obj);
    ~vector_int() { delete []p; cout << "deleted\n"; }
    int & at(int index)const;
    int getsize()const { return size; }
private:
    int* p;
    int size;
};

vector_int::vector_int(int n) {
    p = new int[n] ();
    size = n;
    cout << "已申请"<<n<<"个int大小空间\n";
}

vector_int::vector_int(int n, int value) {
    p = new int[n];
    size = n;
    for (auto i = 0; i < n; i++)
        p[i] = value;
    cout << "已申请"<<n<<"个int大小空间,并且已赋值" << value << endl;
}

vector_int::vector_int(const vector_int& obj) {
    size = obj.getsize();
    p = new int[size];
    for (auto i = 0; i < size; i++)
        p[i] = obj.at(i);
}

int & vector_int::at(int index) const {
    assert(index >= 0 && index < size);
    return p[index];
}
#endif 

 

 

#include<iostream>
#include"1.hpp"

using namespace std;

int main() {
    int n;
    cin >> n;
    vector_int x1(n);

    vector_int x2(n, 42);

    vector_int y(x2);

    y.at(0) = 999;

    for (int i = 0; i < 2; i++)
        cout << endl<<y.at(i) << " ";

    cout << endl;
    
    return 0;
}

 

 

 

 

#ifndef MATRIX_H
#define MATRIX_H

#include <iostream>
#include <cassert>
using namespace std;
class Matrix
{
public:
    Matrix(int n);                     // 构造函数，构造一个n*n的矩阵
    Matrix(int n, int m);              // 构造函数，构造一个n*m的矩阵
    Matrix(const Matrix& X);           // 复制构造函数，使用已有的矩阵X构造
    ~Matrix();                         //析构函数
    void set(const double* pvalue);     // 用pvalue指向的连续内存块数据为矩阵赋值
    void set(int i, int j, int value); //设置矩阵第i行第j列元素值为value
    double& at(int i, int j);          //返回矩阵第i行第j列元素的引用
    double at(int i, int j) const;     // 返回矩阵第i行第j列元素的值
    int get_lines() const;             //返回矩阵行数
    int get_cols() const;              //返回矩列数
    void print() const;                // 按行打印输出矩阵
private:
    int lines; // 矩阵行数
    int cols;  // 矩阵列数
    double* p; // 指向存放矩阵数据的内存块的首地址
};

Matrix::Matrix(int n) {
    lines = cols = n;
    p =new double[n*n];
    cout << "构造一个" << n << "*" << n << "的矩阵" << endl;
}

Matrix::Matrix(int n, int m) {
    lines = n;
    cols = m;
    p =new double[n*m];
    cout << "构造一个" << n << "*" << m << "的矩阵" << endl;
}

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

Matrix::~Matrix() {
    delete[]p;
    cout << "析构函数\n";
}

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

void Matrix::set(int i, int j, int value) {
    p[i * cols + j] = value;
}

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

double Matrix::at(int i, int j) const {
    assert(0 <= i && 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 << endl;
    }
}
#endif

 

 

#include <iostream>
#include "2.hpp"

int main()
{
    using namespace std;

    double x[] = { 1, 2, 3, 4, 5, 6,7,8 };

    Matrix m1(4, 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, 4);
    m2.set(x);
    m2.print();
    cout << "the first line is: " << endl;
    cout << m2.at(0, 0) << " " << m2.at(0, 1) << " " << m2.at(0, 2) <<" " << m2.at(0, 3) << endl;
    cout << endl;

    Matrix m3(m2);
    m3.set(1, 1, 4514);
    m3.print();

    return 0;
}

 

 

 

1 了解动态创建数组的使用方法 T *p=new T[N];程序结束时要及时销毁delete []p;

2 当类中定义了自己的默认构造函数，那么new T()和new T是一样的都是调用自己定义的默认构造函数，但没定义时，new T调用的是系统创建的默认构造函数  new T()还会为基本数据类型和指针类型的成员赋值0且是递归的。

3 数组同2 加（）可以为数组初始化为0