c++ - 我的动态数组有问题

Question

{
    // FIRST ARRAY
    int NumberOfXValues;
    double* FirstArray;
    NumberOfXValues = 0;
    FirstArray = new double[NumberOfXValues];
    // END FIRST ARRAY

    // SECOND ARRAY
    int NumberOfProbabilities;
    double* SecondArray;
    NumberOfProbabilities = 0;
    SecondArray = new double[NumberOfProbabilities];
    // END SECOND ARRAY

    // THIRD ARRAY
    int Product;
    double* ThirdArray;
    Product = 0;
    ThirdArray = new double[Product];
    // END THIRD ARRAY

    // OBTAINING THE NUMBER OF X VALUES
    cout << "Please input the number of \"x\" values we will be using: ";
    cin >> NumberOfXValues;
    // END OF OBTAINING THE NUMBER OF X VALUES

    // OBTAINING THE VALUES IN THE FIRST ARRAY
    int x;
    cout << "Please input the \"x\" values in order from least to greatest: " << endl;
    cout << endl;
    for (int x = 0; x < NumberOfXValues; x++)
    {
        cout << "Enter number: ";
        cin >> FirstArray[x]; 
    }
    cout << endl;
    // END OF OBTAINING THE VALUES IN THE FIRST ARRAY

    // OBTAINING THE VALUES IN THE SECOND ARRAY
    cout << "Please input the probabilities corresponding to their \"x\" values: " << endl;
    cout << endl;
    for (int x = 0; x < NumberOfXValues; x++)
    {
        cout << "Enter probability in decimal form: ";
        cin >> SecondArray[x];
    }
    cout << endl;
    // END OF OBTAINING THE VALUES IN THE SECOND ARRAY

    // MULTIPLYING THE FIRST TWO ARRAYS TO OBTAIN THE THIRD
    for (int x = 0; x < NumberOfXValues; x++)
    {
        ThirdArray[x] = FirstArray[x] * SecondArray[x];
    }
    // END OF MULTIPLYING THE FIRST TWO ARRAYS TO OBTAIN THE THIRD

    //TEST
    for (int x = 0; x < NumberOfXValues; x++)
    {
        cout << ThirdArray[x];
        cout << endl;
    }
    //TEST
}

这是我第一次求助于其中一个网站，但我已经工作了将近一个多小时来解决这个问题。它运行完全平稳，直到它显示第三个数组中的第三个值。它总是给我一个奇怪的数字。

Answer 1

问题是当您创建数组时，您用于大小的变量被设置为 0:

int NumberOfXValues;
double* FirstArray;
NumberOfXValues = 0;
FirstArray = new double[NumberOfXValues];

此处 FirstArray 为 0，因此它将创建一个包含 0 元素的数组。

你必须在获取元素数量后创建数组。

cout << "Please input the number of \"x\" values we will be using: ";
cin >> NumberOfXValues;
FirstArray = new double[NumberOfXValues];