c++ - 如何将偶数复制到数组中并显示它们？

Question

所以我遇到了一些问题，但我不知道是我的代码还是我的编译器导致了这个问题。我的任务是要求用户输入整数，而程序将偶数存储在一个数组中，将赔率存储在另一个数组中。当用户输入 0 时，程序应该向他们显示他们输入了多少偶数和多少赔率，然后列出每个数组中的值。

所以我很快为它写了一个程序，我认为它会工作得很好。没有这样的运气。它总是得到正确的偶数和赔率数，但不是列出数组中的数字，它通常列出用户输入的最后 x 个数字(x 等于该数组中的元素数)。我偶尔也会在输出的末尾出现古怪的 5 位以上的整数。

现在，问题是，我的代码看起来没有任何问题，所以我认为可能是我的编译器造成了问题。

无论如何，这是我的代码:

#include <iostream>
using namespace std;
int main() {
    int input, remainder, even = 0, odd = 0;
    int evenArray[even];
    int oddArray[odd];
    cout << "This program accepts integers until you enter 0.\nPlease enter a value: ";
    cin >> input;
    while (input != 0) {
        remainder = input % 2;
        if (remainder == 0) {
            evenArray[even] = input;
            even++;
        }
        else {
            oddArray[odd] = input;
            odd++;
        }
        cout << "Enter another integer: ";
        cin >> input;
    }
    cout << "\nThe number of evens is " << even << ".\n";
    cout << "The even values are: ";
    for(int i = 0; i < even; i++) {
        cout << evenArray[i] << " ";
    }
    cout << endl;
    cout << "The number of odds is " << odd << ".\n";
    cout << "The odd values are: ";
    for(int i = 0; i < odd; i++) {
        cout << oddArray[i] << " ";
    }
}

这是一个正在运行的例子:

This program accepts integers until you enter 0.
Please enter a value: 1
Enter another integer: 2
Enter another integer: 3
Enter another integer: 4
Enter another integer: 5
Enter another integer: 5
Enter another integer: 3
Enter another integer: 2
Enter another integer: 4
Enter another integer: 6
Enter another integer: 4
Enter another integer: 3
Enter another integer: 0

The number of evens is 6.
The even values are: 2 4 2 4 6 3 
The number of odds is 6.
The odd values are: 2 4 2 4 1912356720 32767

如果有人能告诉我这里的问题是什么，我将不胜感激。

Answer 1

对于初学者来说，可变长度数组不是标准的 C++ 功能，而且您不能像这样声明元素数等于 0 的数组

int input, remainder, even = 0, odd = 0;
int evenArray[even];
int oddArray[odd];

这样的声明是没有意义的。

如果数组的大小在编译时未知，则使用标准容器 std::vector。

这是一个演示程序

#include <iostream>
#include <vector>

int main()
{
    using namespace std;

    std::vector<int> evenArray, oddArray;
    int input;

    cout << "This program accepts integers until you enter 0.\nPlease enter a value: ";

    while ( cin >> input and input != 0 ) 
    {
        if ( input % 2 == 0) 
        {
            evenArray.push_back( input );
        }
        else 
        {
            oddArray.push_back( input );
        }

        cout << "Enter another integer: ";
    }

    cout << "\nThe number of evens is " << evenArray.size() << ".\n";
    cout << "The even values are: ";
    for ( int x : evenArray ) 
    {
        cout << x << ' ';
    }
    cout << endl;

    cout << "The number of odds is " << oddArray.size() << ".\n";
    cout << "The odd values are: ";
    for ( int x : oddArray ) 
    {
        cout << x << ' ';
    }
    cout << endl;

    return 0;
}

另一种方法是声明一些固定最大大小的数组，并限制用户输入的元素不能超过给定的最大值。例如

#include <iostream>

int main()
{
    using namespace std;

    const size_t N = 100;

    int evenArray[N], oddArray[N];
    size_t even = 0, odd = 0;

    cout << "This program accepts integers until you enter 0.\nPlease enter a value: ";

    int input;

    while ( even < N and odd < N and cin >> input and input != 0 )
    {
        if ( input % 2 == 0) 
        {
            evenArray[even++] = input;
        }
        else 
        {
            oddArray[odd++] = input;
        }

        cout << "Enter another integer: ";
    }

    cout << "\nThe number of evens is " << even << ".\n";
    cout << "The even values are: ";
    for ( size_t i = 0; i < even; i++ ) 
    {
        cout << evenArray[i] << ' ';
    }
    cout << endl;

    cout << "The number of odds is " << odd << ".\n";
    cout << "The odd values are: ";
    for (size_t i = 0; i < odd; i++)
    {
        cout << oddArray[i] << ' ';
    }
    cout << endl;

    return 0;
}