Question

我读过的所有内容都说这应该很简单，你只需要添加这三行

typedef double* DoublePtr;
  DoublePtr p;
  p = new double [10]

但我在哪里添加此代码？我试过的一切都打破了我的计划我错过了什么？我尝试了一个set函数来设置max size的值，但它也没有用有谁知道怎么做？

#include<iostream>
using namespace std;
const int MAX_SIZE = 50;

class ListDynamic
{

    public:

        ListDynamic();
        bool full();
        int getSize();
        void addValue(double value);
        double getValue(int index);
        double getLast();
        void deleteLast();
        friend ostream& operator <<(ostream& out, const ListDynamic& thisList);  

    private:
        double listValues[MAX_SIZE];
        int size;
};
int main()
{
    double value;
    ListDynamic l;
    cout << "size of List " << l.getSize() << endl;



    cout << "New size of List " << l.getSize() << endl;
    cout << "First Value: " << l.getValue(0) << endl;
    cout << "Last Value: " << l.getLast() << endl;
    cout << "deleting last value from list" << endl;
    l.deleteLast();
    cout << "new list size "  << l.getSize() << endl;
    cout << "the list now contains: " << endl << l << endl;
    system("pause");
    return 0;
}

ListDynamic::ListDynamic()
{
    size = 0;
}

bool ListDynamic::full()
{
    return (size == MAX_SIZE);
}

int ListDynamic::getSize()
{
    return size;
}

void ListDynamic::addValue(double value)
{
    if (size < MAX_SIZE)
    {
        listValues[size] = value;
        size++;
    }
    else
        cout << "\n\n*** Error in ListDynamic Class: Attempting to add value past max limit.";
}

double ListDynamic::getValue(int index)
{
    if (index < size)
        return listValues[index];
    else
        cout << "\n\n*** Error in ListDynamic Class: Attempting to retrieve value past current size.";
}
double ListDynamic::getLast()
{
    if (size > 0)
        return getValue(size - 1);
    else
        cout << "\n\n*** Error in ListDynamic Class: Call to getLast in Empty List.";
}

void ListDynamic::deleteLast()
{
    if (size > 0)
        size--;
    else
        cout << "\n\n*** Error in ListDynamic Class: Call to deleteLast in Empty List.";
}
ostream& operator <<(ostream& out, const ListDynamic& thisList)
{
    for (int i = 0; i < thisList.size; i++)
        out << thisList.listValues[i] << endl;
    return out;
}

Answer 1

您需要将listValues更改为double*

double* listValues;

当你添加一个大于这个大小的值时，你需要重新分配你的数组的数组，并将前一个数组的元素复制到新数组。例如：

void ListDynamic::addValue(double value)
{
    if (full())
    {
        double* temp = new double[size];
        std::copy(listValues, listValues + size, temp);

        delete[] listValues;
        listValues = new double[size + 1];

        std::copy(temp, temp + size, listValues);
        listValues[size] = value;
        delete[] temp;
    } else
    {
        listValues[size++] = value;
    }
}

更改数组类以保存动态数组

1 个答案: