实验六模板类和文件I/O

task3.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();
}

#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";
}

修改前：

修改后：

原因分析：写入数据时以int类型写入，每个数据占用四个字节，以char类型输出时每个数据占据一个字节，因此产生三个空字节，输出为空白

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();
}

Vector.hpp

#pragma once
#include<bits/stdc++.h>

using namespace std;

template<typename T> 
class Vector{
    public:
        Vector(int n):size{n}{    
            p=new T[n];
        }
        Vector(int n,int value):size{n}{
            p=new T[size];
            for(int i=0;i<n;i++){
                p[i]=value;
            }
        }
        Vector(const Vector &obj):size{obj.size}{
            p=new T[size];
            for(int i=0;i<size;i++){
                p[i]=obj.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 i){
            return p[i];
        }
        friend void output(Vector &obj){
            for(int i=0;i<obj.size-1;i++){
                cout<<obj.p[i]<<" ";
            }
            cout<<obj.p[obj.size-1]<<endl;
        }
    private:
    T *p;
    int size;
};

测试结果截图：

task5.cpp

#include<bits/stdc++.h>
#include<iomanip>
using namespace std;

void output(ofstream &out){
    out.open("cipher_key.txt",ios::app);
    if(!out.is_open()){
        cout<<"fail to open cipher_key.txt"<<endl;
    }
    for(int i=0;i<=26;i++){
        if(i==0){
            cout<<"   ";
            out<<setw(2)<<left<<"   ";
        }else{
            cout<<setw(3)<<left<<i;
            out<<setw(3)<<left<<i;
        }
        for(int j=65;j<=90;j++){
            if(i==0){
                char x=j+32;
                cout<<setw(2)<<left<<x;
                out<<setw(2)<<left<<x;  
            }else{
                char x=(i+j-65)%26+65;
                cout<<setw(2)<<left<<x;
                out<<setw(2)<<left<<x;
            }
        }
        cout<<endl;
        out<<endl;
    }
    out.close();
}

int main(){
    ofstream out;
    output(out);    
    return 0;
}