2022.11.30 OOP实验

实验6 模板类和文件IO

任务3

task36_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();
}

运行结果：

task36_2.cpp

#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;
    }

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

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

运行结果：

修改过后：

#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";
}

运行结果：

分析：
a的ASCII码为97，所以97->a
<int,5>占20个字节，<char,5>占5个字节，int型转成char型时多余的三个字节转成空格
b的ASCII码为98，所以98->a

任务4

Vector46.hpp

#pragma once
#include<iostream>
#include<cassert>

using namespace std;

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

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

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

    ~Vector() {
        delete[] p;
    }

    int get_size() { 
        return size; 
    }

    T& at(int index) {
        assert(index >= 0 && index < size);
        return p[index];
    }

    T& operator[](int index) {
        assert(index >= 0 && index < size);
        return p[index];
    }

    template<typename T1>
    friend void output(const Vector<T1>& v);
private:
    int size;
    T* p;
};

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

tesk46.cpp

#include <iostream>
#include "Vector46.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();
}

运行结果：

任务5

task56.cpp

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

using namespace std;

void output(std::ostream& out) {
    char a[26][26];
    cout << "   ";
    out << "   ";
    for (char i = 'a'; i <= 'z'; i++) {
        cout << i << " ";
        out << i << " ";
    }
    cout << endl;
    out << endl;

    for (int i = 0; i < 26; i++) {
        for (int j = 0; j < 26; j++) {
            a[j][i] = 'A' + char((j + i ) % 26);
        }
    }
    for (int i = 0; i < 26; i++) {
        cout << setw(2) << i + 1;
        out << setw(2) << i + 1;
        for (int j = 0; j < 26; j++) {
            cout  << setw(2)  << setfill(' ') << a[i][j];
            out  << setw(2)  << setfill(' ') << a[i][j];
        }
        cout << endl;
        out << endl;
    }
}
int main() {
    ofstream out;
    out.open("cipher_key.txt");
    if (!out.is_open()) {
        cout << "fail to open file ans.txt to write" << endl;
        return 1;
    }
    output(out);
    out.close();
}

运行结果：