解释这行代码int row = (int)_msize(arr) / (int)sizeof(double*);

这行代码的作用是计算一个二维数组的行数。具体来说：

- `_msize(arr)` 函数返回指向 `arr` 所指向的内存块的大小，以字节为单位。
- `(int)sizeof(double*)` 计算 `double*` 类型在当前平台上的大小，以字节为单位。
- `_msize(arr) / (int)sizeof(double*)` 计算 `arr` 所指向的内存块中能容纳多少个 `double*` 类型的指针，也就是二维数组的行数。
- 最后将结果转换为整型，赋值给 `row` 变量。

相关问题

Polynomial::Polynomial(const Polynomial& a) { this->mNmb = a.mNmb; mCount++; delete[] this->mXs; delete[] this->mJi; this->mXs = a.mXs; this->mJi = a.mJi; this->mSize = a.mSize; } Polynomial::~Polynomial() //析构函数 { mCount--; //多项式个数-1 //这里不释放内存，否则在运算符重载部分会出错，内存的释放需要手动释放 } void Polynomial::release() { if (mXs) { delete[] mXs; mXs = 0; } if (mJi) { delete[] mJi; mJi = 0; } } void Polynomial::add(int xs, int mj) //增加多项式 { if (mNmb >= mSize) { mSize += 10; //扩容 mXs = (int*)realloc(mXs, sizeof(int) * mSize); mJi = (int*)realloc(mJi, sizeof(int) * mSize); } mXs[mNmb] = xs; mJi[mNmb] = mj; mNmb++; Sort(); }

这段代码实现了多项式类的拷贝构造函数和析构函数，以及增加多项式的函数。其中，拷贝构造函数用于创建一个新的多项式对象并将其初始化为另一个多项式对象的副本，析构函数用于释放多项式对象所占用的内存，而增加多项式的函数则用于在多项式对象中添加新的多项式项。需要注意的是，增加多项式项时会自动进行排序。另外，这里使用了realloc函数来动态扩展数组大小，所以在释放内存时需要使用delete[]而不是free函数。

将以下程序补充完整 #include <iostream> #include <fstream> #include <iomanip> using namespace std; template <typename ElemType> class myArrayList { private: int mSize; int mLen; ElemType *mpArr; public: myArrayList(int n); myArrayList(ElemType *a,int n); void show(); ElemType getMax(); //以下函数由同学完成 //void sort(); //myArrayList(myArrayList<ElemtType> &other);//拷贝构造函数 //mymyArrayList<ElemType> & operator =(mymyArrayList<ElemType> &other) }; template <typename ElemType> myArrayList<ElemType>::myArrayList(int n) { this->mSize=n; this->mLen=0; this->mpArr=new ElemType[mSize]; } template <typename ElemType> myArrayList<ElemType>::myArrayList(ElemType *a,int n) { this->mSize=n; this->mLen=n; this->mpArr=new ElemType[mSize]; for(int i=0;i<mLen;i++) mpArr[i]=a[i]; } template <typename ElemType> void myArrayList<ElemType>::show() { for(int i=0;i<mLen;i++) cout<<setw(4)<<mpArr[i]; cout<<endl; } template <typename ElemType> ElemType myArrayList<ElemType>::getMax() { ElemType max; max=mpArr[0]; for(int i=1;i<mLen;i++) if(max<mpArr[i]) max=mpArr[i]; return max; } //Student.h class Student { private: int mId; float height; int score; public: Student(int id=0,float h=0,int s=0):height(h),mId(id),score(s) { } friendbool operator <(Student &a1,Student &a2) { if(a1.height<a2.height) return true; else return false; } friend ostream &operator <<(ostream &out,Student &s) { out<<"ID:"<<s.mId<<" Height:"<<s.height<<" Socre:"<<s.score<<endl; return out; } }; //主程序 int main() { int a[]={1,2,3,5,7,9,12,8}; double b[]={1,2.5,3.6,5,7,9,12.8,8}; myArrayList <int> list1(a,8); list1.show(); cout<<"max="<<list1.getMax()<<endl; myArrayList <double> list2(b,8); list2.show(); cout<<"max="<<list2.getMax()<<endl; Student s[3]={Student(1,175,80),Student(2,178,90),Student(3,195,83)},s1; myArrayList <Student> list3(s,3); list3.show(); cout<<"max="<<list3.getMax()<<endl; } 说明： 将以下程序补充完整 //void sort(); //myArrayList(myArrayList<ElemtType> &other);//拷贝构造函数 //mymyArrayList<ElemType> operator =(mymyArrayList<ElemType> &other) //修改补充 Student类，要求按成绩排序（从高到低）并将完整的代码发出来

以下是补充完整的程序：

#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;

template <typename ElemType>
class myArrayList {
private:
    int mSize;
    int mLen;
    ElemType *mpArr;
public:
    myArrayList(int n);
    myArrayList(ElemType *a,int n);
    void show();
    ElemType getMax();
    void sort();
    myArrayList(const myArrayList<ElemType> &other);
    myArrayList<ElemType> & operator =(const myArrayList<ElemType> &other);
};

template <typename ElemType>
myArrayList<ElemType>::myArrayList(int n) {
    this->mSize=n;
    this->mLen=0;
    this->mpArr=new ElemType[mSize];
}

template <typename ElemType>
myArrayList<ElemType>::myArrayList(ElemType *a,int n) {
    this->mSize=n;
    this->mLen=n;
    this->mpArr=new ElemType[mSize];
    for(int i=0;i<mLen;i++)
        mpArr[i]=a[i];
}

template <typename ElemType>
void myArrayList<ElemType>::show() {
    for(int i=0;i<mLen;i++)
        cout<<setw(4)<<mpArr[i];
    cout<<endl;
}

template <typename ElemType>
ElemType myArrayList<ElemType>::getMax() {
    ElemType max;
    max=mpArr[0];
    for(int i=1;i<mLen;i++)
        if(max<mpArr[i])
            max=mpArr[i];
    return max;
}

template <typename ElemType>
void myArrayList<ElemType>::sort() {
    for(int i=0;i<mLen-1;i++) {
        for(int j=0;j<mLen-i-1;j++) {
            if(mpArr[j]<mpArr[j+1]) {
                ElemType tmp=mpArr[j];
                mpArr[j]=mpArr[j+1];
                mpArr[j+1]=tmp;
            }
        }
    }
}

template <typename ElemType>
myArrayList<ElemType>::myArrayList(const myArrayList<ElemType> &other) {
    this->mSize=other.mSize;
    this->mLen=other.mLen;
    this->mpArr=new ElemType[mSize];
    for(int i=0;i<mLen;i++)
        mpArr[i]=other.mpArr[i];
}

template <typename ElemType>
myArrayList<ElemType> & myArrayList<ElemType>::operator =(const myArrayList<ElemType> &other) {
    if(this==&other)
        return *this;
    delete []mpArr;
    this->mSize=other.mSize;
    this->mLen=other.mLen;
    this->mpArr=new ElemType[mSize];
    for(int i=0;i<mLen;i++)
        mpArr[i]=other.mpArr[i];
    return *this;
}

class Student {
private:
    int mId;
    float height;
    int score;
public:
    Student(int id=0,float h=0,int s=0):height(h),mId(id),score(s) { }
    friend bool operator <(Student &a1,Student &a2) {
        if(a1.score<a2.score)
            return true;
        else
            return false;
    }
    friend ostream &operator <<(ostream &out,Student &s) {
        out<<"ID:"<<s.mId<<" Height:"<<s.height<<" Socre:"<<s.score<<endl;
        return out;
    }
};

int main() {
    int a[]={1,2,3,5,7,9,12,8};
    double b[]={1,2.5,3.6,5,7,9,12.8,8};
    myArrayList <int> list1(a,8);
    list1.show();
    cout<<"max="<<list1.getMax()<<endl;
    myArrayList <double> list2(b,8);
    list2.show();
    cout<<"max="<<list2.getMax()<<endl;
    Student s[3]={Student(1,175,80),Student(2,178,90),Student(3,195,83)},s1;
    myArrayList <Student> list3(s,3);
    list3.show();
    list3.sort();
    cout<<"max="<<list3.getMax()<<endl;
    list3.show();
    return 0;
}

在这个程序中，我们添加了以下功能：

- `sort()`函数用于对数组进行排序
- 拷贝构造函数 `myArrayList(const myArrayList<ElemType> &other)`用于创建新的对象并将其初始化为与另一个对象相同的值
- 赋值运算符 `myArrayList<ElemType> & operator =(const myArrayList<ElemType> &other)`用于将一个对象的值赋给另一个对象

此外，我们还修改了`Student`类的实现，使其能够按照成绩从高到低进行排序。