实验六

task3_1.cpp

#include <iostream>
#include <fstream>
#include <array>
#define N 5

int main() {
    using namespace std;

    array<int, N> x {97, 98, 99, 100, 101};

    ofstream out;
    out.open("data1.dat", ios::binary);
    if(!out.is_open()) {
        cout << "fail to open data1.dat\n";
        return 1;
    }

    out.write(reinterpret_cast<char *>(&x), sizeof(x));
    out.close();
}

task3_2.cpp

#include <iostream>
#include <fstream>
#include <array>
#define N 5

int main() {
    using namespace std;
    array<char, N> x;

    ifstream in;
    in.open("data1.dat", ios::binary);
    if(!in.is_open()) {
        cout << "fail to open data1.dat\n";
        return 1;
    }

    in.read(reinterpret_cast<char *>(&x), sizeof(x));
    in.close();

    for(auto i = 0; i < N; ++i)
        cout << x[i] << ", ";
    cout << "\b\b \n";
}

 char型占用1字节，int型占用4个字节。转换成char字符时，a只占1个字符，所以产生空格。

Vector.hpp

#include<iostream>
using namespace std;
template<typename T>

class Vector{
public:
    Vector(int n); 
    Vector(int n,T value);
    Vector(const Vector<T>& v);
        
    T get_size();
    T& at(int index);
    T& operator[](int i);
        
    template<typename A>
    friend void output(const Vector<A>& v);
        
private:
    int size;
    T *p;
};

template<typename T>
Vector<T>::Vector(int n):size{n}
{
    p=new T[n];
}

template<typename T>
Vector<T>::Vector(int n,T value):size{n}
{
    p=new T[n];
    for(auto i=0;i<size;i++)
        p[i]=value;
}

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

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

template<typename T>
T& Vector<T>::at(int index)
{
    return p[index];
}

template<typename T>
T& Vector<T>::operator[](int i)
{    
    return p[i];
}

template<typename A>
void output(const Vector<A>& v)
{
    for(auto i=0;i<v.size;i++)
        cout<<v.p[i]<<", ";
        cout<<"\b\b \n";
}

task4.cpp

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

void test() {
    using namespace std;

    int n;
    cin >> n;
    
    Vector<double> x1(n);
    for(auto i = 0; i < n; ++i)
        x1.at(i) = i * 0.7;

    output(x1);

    Vector<int> x2(n, 42);
    Vector<int> x3(x2);

    output(x2);
    output(x3);

    x2.at(0) = 77;
    output(x2);

    x3[0] = 999;
    output(x3);
}

int main() {
    test();
}

task5.cpp

#include<iostream>
#include<fstream>
#include<iomanip>
using namespace std;

void output(std::ostream& output)
{
output << " ";
for (int i = 97; i < 123; i++)
{
output << setw(2) << char(i);
}
output << endl;

for (int i = 1; i <= 26; i++)
{
output << setw(2) << i;
int j;
for (j=i;j<i+26;j++)
{
output<<setw(2)<<char(65+j%26);
}
output << endl;
}
}

int main()
{
ofstream out;
output(cout);
out.open("cipher_key.txt");
output(out);
return 0;
}