实验六 模板类和文件I/O

task3_1:

#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;
    }
    
    //把从地址&x开始连续sizeof(x)个字节的数据块以字节数据块方式写入data1.txt
    out.write(reinterpret_cast<char *>(&x), sizeof(x));
    out.close();   
} 

task3_2:

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

int main() {
    using namespace std;
    
    array<int, N> x;
    
    ifstream in;
    in.open("data1.dat", ios::binary);
    if(!in.is_open()) {
        cout << "fail to open data1.dat\n";
        return 1;
    }
    
    //从文件流对象in关联的文件data1.dat中读取sizeof(x)字节数据写入&x开始的地址单元
    in.read(reinterpret_cast<char *>(&x), sizeof(x));
    in.close();
    
    for(auto i = 0; i < N; ++i) 
        cout << x[i] << ", ";
    cout << "\b\b \n"; 
}

 

 修改后：

 

 分析：

char型占1个字节，而int型占4个字节，导致输出3个空格且b出现在第5个位置

 

task4.hpp：

#pragma once

#include <iostream>
#include <cassert>
#include <string>

using namespace std;

template<typename T>
class Vector {
    public:
    Vector(int n0);
    Vector(int n0, T value0);
    Vector(const Vector<T> &v);
    ~Vector();
    
    T &at(int i);
    int get_size() { return n; };
    T& operator[](int i);
    
    template<typename T1>
    friend void output(Vector<T1> &v);    
    
    private:
    int n;
    T *p;
};

template<typename T>
Vector<T>::Vector(int n0) : n{n0} {
    p = new T[n0];
}

template<typename T>
Vector<T>::Vector(int n0, T value0) : n{n0} {
    p = new T[n];
    for(auto i = 0;i <= n; i++)
        p[i] = value0;
}

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

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

template<typename T>
T &Vector<T>::at(int i) {
    assert(i >= 0 && i < n);
    return p[i];
} 

template<typename T1>
void output(Vector<T1> &v){
    for(auto i = 0; i < v.n; i++)
    cout << v.p[i] << " ";
    cout << endl;
}

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

task4.cpp:

#include <iostream>
#include "实验六task4_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

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

using namespace std;

void put(std::ostream &out, int n, char a) {
    char A = 'A';
    int i = 0;
    cout << n;
    out << n;
    for(;a <= 'Z'; a++)
    {
       cout << setw(2) << a;
       out << setw(2) << a;
       i++;    
    }
    for(;i < 26; i++, A++)
    {
       cout << setw(2) << A;
       out << setw(2) << A;
    }
}

void output(std::ostream &out) {
    char k = 'a', K = 'B';
    cout << "  ";
    out << "  ";
    for(;k <= 'z'; k++)
    {
       cout << setw(2) << k;
       out << setw(2) << k;    
    }
    cout << endl;
    out << endl;
    for(int i = 1; i <= 26; i++, K++) {
        if(i < 10)
           cout << " ";
           out << " ";
        put(out,i,K);
        cout << endl;
        out << endl;
    }
    
}

int main() {
    ofstream out;
    
    out.open("cipher_key.txt", ios::out);
    if(!out.is_open()) {
        cout << "fail to open chipher_key\n";
        return 1;
    }
    output(out);
    out.close();
}