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<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:
改动后:
原因:
in.write(reinterpret_cast<char*>(&x), sizeof(x)),输入时,x是int类型,读取时也是int类型,int占四个字节,而char每次只读一个字符,因此修改后读取a后,又读取了三个空格,之后接着读b。
Task4:
Vector.hpp
#pragma once #include<iostream> #include<cassert> using namespace std; template<typename T> class Vector { public: Vector(int n); Vector(int n, int v); Vector(const Vector<T>& x); ~Vector() = default; int get_size() { return size; } T& at(int i); T& operator[](int i); template<typename T1> friend void output(const Vector<T1>& x); private: T* p; int size; }; template<typename T> Vector<T>::Vector(int n) :size{ n } { p = new T[size]; } template<typename T> Vector<T>::Vector(int n, int v) : size{ n } { p = new T[size]; for (int i = 0; i < size; i++) p[i] = v; } template<typename T> Vector<T>::Vector(const Vector<T>& x) { size = x.size; p = new T[size]; for (int i = 0; i < size; i++) p[i] = x.p[i]; } template<typename T> T& Vector<T>::at(int i) { assert(i >= 0 && i < size); return p[i]; } template<typename T> T& Vector<T>::operator[](int i) { assert(i >= 0 && i < size); return p[i]; } template<typename T1> void output(const Vector<T1>&x) { for (int i = 0; i < x.size; i++) { cout << x.p[i] << ","; } cout << "\b " << endl; }
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 * 1.3; output(x1); Vector<int> x2(n, 42); Vector<int> x3(x2); output(x2); output(x3); x2.at(0) = 25; output(x2); x3[0] = 897; output(x3); } int main() { test(); }
运行结果:
Task5:
task5.cpp
#include<iostream> #include<fstream> #include<iomanip> using namespace std; void output(std::ostream& out) { char a[26][26]; cout << " "; out << " "; for (char i = 'a'; i <= 'z'; i++) { cout << setw(2) << i; out << setw(2) << i; } cout << endl; out << endl; for (int i = 0; i < 26; i++) { cout << setw(2) << i + 1; out << setw(2) << i + 1; for (int j = 0; j < 26; j++) { a[i][j] = (char)(65 + (i + j + 1) % 26); cout << setw(2) << a[i][j]; out << setw(2) << a[i][j]; } cout << endl; out << endl; } } int main() { ofstream out; out.open("cipher_key.txt"); if (!out.is_open()) { cout<<"fail to open cipher_key.txt."<<endl; return 1; } output(out); out.close(); }
运行结果: