Question

所以我一直很难解决这个问题。我的所有代码当前都可以正常工作，除了最后一个模块，在该模块中，我试图比较两个数组的差异并将问题编号记录到一个新数组中。我不太确定该如何设置。任何帮助将不胜感激。

主要问题是我创建的数组不正确。我不知道如何设置一个空白数组，该数组在输入值时会变大。除非我真的把这个概念搞砸了。在尝试其他事情时，我当前已将问题注释掉。

#include <iostream>
using namespace std;

const int COLS = 20;
void input_data(char [], int);
void compare_data(char [], int, char [], int);

int main()
{
    char letters[COLS];
    char answers[] = { 'A', 'D', 'B', 'B',
                       'C', 'B', 'A', 'B',
                       'C', 'D', 'A', 'C',
                       'D', 'B', 'D', 'C',
                       'C', 'A', 'D', 'B'};

    input_data(letters, COLS);
    compare_data(letters, COLS, answers, COLS);
}

void input_data(char letter[], int size)
{
    cout << "Please enter the student's answers for each of the questions. \n";
    cout << "Press Enter after typing each answer. \n";
    cout << "Please enter only an A, B, C, or D for each question. \n";
    for (int i = 1; i <= size; i++)
    {
        cout << "Question " << i << ": ";
        cin >> letter[i - 1];
        while (letter[i - 1] != 'A' && 
                letter[i - 1] != 'B' &&
                letter[i - 1] != 'C' &&
                letter[i - 1] != 'D')
        {
            cout << "Please enter only A, B, C, or D \n";
            cout << "Question " << i << ":";
            cin >> letter[i - 1];
        }
    }
}

void compare_data(char letter[], int size, char answer[], int cols)
{
    int ans_correct = 0;
    int ans_wrong = 0;
    //int incorrect[20];
    for (int i = 1; i <= size; i++)
    {
        if (letter[i] == answer[i])
            ans_correct += 1;
        else
        {
            ans_wrong += 1;
            //incorrect[i-1] = i;
        }
    }

    if (ans_correct >= 15)
        cout << "The student passed the exam. \n";
    else
        cout << "The student did not pass the exam. \n";

    cout << "Correct Answers: " << ans_correct << endl;
    cout << "Incorrect Answers: " << ans_wrong << endl << endl;

    cout << "Questions that were answered incorrectly: \n";
    for (int i = 1; i < size; i++)
    {
        //cout << incorrect[i-1] << endl;
    }
}

Answer 1

好的，这是有效的版本。它不会增长不正确的数组，因为对于这么小的操作而言，这是过大的选择，而且无论如何您都在使用常量'COLS'。

由于这是一个用c ++标记的问题，如果您真的想要一个动态数组，为什么不使用std :: vector？您可以使用C样式的数组做类似的事情，但这很混乱。

void compare_data(char letter[], int size, char answer[], int cols)
{
   int ans_correct = 0;
   int ans_wrong = 0;
   //setup array big enough to hold all answers
   //and initialize to 0
   int incorrect[COLS] = {0};
   // Your original code had wrong loop limits!
   for (int i = 0; i < size; i++)
   {
     if (letter[i] == answer[i])
        ans_correct += 1;
     else
     {
        //Fill in incorrect only on wrong answers!
        //But the number you want to record is the
        //the number of the question, which is i + 1
        incorrect[ans_wrong] = i + 1;
        ans_wrong += 1;
    }
}

if (ans_correct >= COLS/2)
    cout << "The student passed the exam. \n";
else
    cout << "The student did not pass the exam. \n";

cout << "Correct Answers: " << ans_correct << endl;
cout << "Incorrect Answers: " << ans_wrong << endl << endl;

cout << "Questions that were answered incorrectly: \n";
//Even if the array is bigger, you don't wnat to output the
//unused parts
for (int i = 0; i < ans_wrong; i++)
{
    cout << incorrect[i] << endl;
}
}

取两个数组中的差异，并在第三个数组中记录其编号

1 个答案: