task3:
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"; }
测试结果截图:
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:
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:
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; }
测试结果截图: