一次C++作业（模板类的构造& C++的I/O流类库）1

1．理解下面的动态数组类模板，它由一系列位置连续、任意数量相同类型的元素组成，其元素个数可在程序运行时改变，并完成该类中没有完成的成员函数（不允许改变已有代码），并设计主函数，实现对该模板类的功能测试。

#include<iostream>
#include<stdlib.h>
using namespace std;
//容错处理
enum ErrorType {
	invalidArraySize, memoryAllocatetionError, indexOutOfRang
};
const char* errorMsg[] = { "invalid Array Size",",memory Allocatetion Error","indexOutOfRang" };
template<class T>
class Array {
private:
	T* alist;
	int size;
	void Error(ErrorType error) const //输出错误信息
	{
		cout << errorMsg[error] << endl;
	}
public:
	Array(int sz = 50);//构造函数
	Array(const Array<T>& X);//拷贝构造函数
	~Array(void);//析构函数
	Array<T>& operator=(const Array<T>& rhs);//重载赋值运算符
	T& operator[](int i);//重载下标运算符
	int getsize(void) const;//获取数组大小
	void resize(int sz);//重新设置数组大小
};
template<class T>
Array<T>::Array(int sz) {
	if (sz <= 0) {
		Error(invalidArraySize);//返回值void
	}
	size = sz;
	alist = new T[size];//错误会null或0
	if (alist == 0) {
		Error(memoryAllocatetionError);//返回值void
	}
}
template<class T>
Array<T>::Array(const Array<T>& X) {
	int n = X.size;
	size = n;
	alist = new T[n];
	if (alist == 0) {
		Error(memoryAllocatetionError);
	}
	T* srcptr = X.alist;
	T* destptr = alist;
	while (n--) {
		*destptr++ = *srcptr++;
	}
}
template<class T>
Array<T>::~Array() {
	delete[]alist;
}
template<class T>
Array<T>& Array<T>:: operator=(const Array<T>& rhs) {
	int n = rhs.size;
	if (size != n) {//比较左右长度
		delete[] alist;
		alist = new T[n];
		if (alist == 0) {
			Error(memoryAllocatetionError);
		}		
	}
	size = n;
	T* destptr= alist;
	T* srcptr = rhs.alist;
	while (n--) {
		*destptr++ = *srcptr++;
	}
	return *this;
}
template<class T>
T& Array<T>::operator[](int n) {
	if (n<0 || n>size - 1) {
		Error(indexOutOfRang);
	}
	return alist[n];
}

template<class T>
int Array<T>::getsize(void)const {
	return size;
}
template<class T>
void Array<T>::resize(int sz) {
	size = sz;
	delete alist;
	alist = new T[size];//new 分空间
}
int main() {
	int i;
	int n1, n2;
	cout << "请分别输入数组a1,a2的长度";
	cin >> n1 >> n2;
	Array<int> a1(n1), a2(n2);
	cout << "请输入a1数组的数字成员：";
	for (i = 0; i < a1.getsize(); i++) {
		cin >> a1[i];
	}
	cout << "数组a1为：";
	for (i = 0; i < a1.getsize(); i++) {
		cout << a1[i] << "  ";
	}
	cout << endl;
	cout << "将数组a1的值复制到a2中" << endl;;
	a2 = a1;
	cout << "数组a2为：";
	for (i = 0; i < a1.getsize(); i++) {
		cout << a2[i] << "  ";
	}
	cout << endl;
	cout << "现在更改数组a1的长度，请输入修改后的长度：";
	int m;
	cin >> m;
	a1.resize(m);
	cout << "请输入" << m << "个数" << endl;
	for (i = 0; i < a1.getsize(); i++) {
		cin >> a1[i];
	}
	cout << "现在数组a1为：";
	for (i = 0; i < a1.getsize(); i++) {
		cout << a1[i] << "  ";
	}
}

2．阅读下列程序，然后上机运行验证输出结果，并回答下列问题。

#include<iostream>
using namespace std;

void showflags(long f)
{
	long i = 0x8000;
	for (; i; i = i >> 1)
	{
		if (i & f)
			cout << "1";
		else
			cout << "0";
	}
	cout << endl;
}
void main()
{
	showflags(cout.flags());
	cout << "x_width=" << cout.width() << endl;
	cout << "x_fill=" << cout.fill() << endl;
	cout << "x_precision=" << cout.precision() << endl;
	cout << 123 << " " << 123.45678 << "
";
	cout << "-------------" << endl;
	cout << "* * * x_width=10,x_fill= ,x_precision=4 * * *" << endl<<endl<<endl<<endl;
	cout.width(10);
	cout.precision(4);
	cout << 123 << " " << 123.45678 << " " << 234.567 << endl;//1

	cout << "x_width=" << cout.width() << endl;
	cout << "x_fill=" << cout.fill() << endl;
	cout << "x_precision=" << cout.precision() << endl;
	cout << "-------------" << endl;
	cout << "* * * x_width=10,x_fill=&,x_precision=4 * * *" << endl;
	cout.fill('&');
	cout.width(10);
	cout << 123 << " " << 123.45678 << endl;
	cout.setf(ios::left);
	cout.width(10);
	cout << 123 << " " << 123.45678 << endl;
	cout << "x_width=" << cout.width() << endl;
	cout << "x_fill=" << cout.fill() << endl;
	cout << "x_precision=" << cout.precision() << endl<<endl<<endl;
	showflags(cout.flags());//2

	cout.setf(ios::right | ios::unitbuf);
	cout << endl << endl << endl;
	showflags(cout.flags());//3

}

   123     123.5     234.6
   0000001001000001
   0000001011000011