Question

我遇到将2D数组传递给c ++函数的问题。该函数应该打印2D数组的值。但是得到错误在功能void showAttributeUsage(int)中数组下标的int（int）类型无效我知道问题在于我将特定数组传递给函数的语法，但我不知道如何解决这个特定问题。
代码：

#include <iostream>

using namespace std;
void showAttributeUsage(int);
int main()
{
    int qN, aN;
    cout << "Enter Number of Queries : ";
    cin >> qN;
    cout << "\nEnter Number of Attributes : ";
    cin >> aN;
    int attVal[qN][aN];
    cout << "\nEnter Attribute Usage Values" << endl;
    for(int n = 0; n < qN; n++) { //for looping in queries
        cout << "\n\n***************** COLUMN " << n + 1 << " *******************\n\n";
        for(int i = 0; i < aN; i++) {     //for looping in Attributes
LOOP1:
            cout << "Use(Q" << n + 1 << " , " << "A" << i + 1 << ") = ";
            cin >> attVal[n][i];
            cout << endl;
            if((attVal[n][i] > 1) || (attVal[n][i] < 0)) {
                cout << "\n\nTHE VALUE MUST BE 1 or 0 . Please Re-Enter The Values\n\n";
                goto LOOP1;                  //if wrong input value
            }

        }

    }
    showAttributeUsage(attVal[qN][aN]);
    cout << "\n\nYOUR ATTRIBUTE USAGE MATRIX IS\n\n";

    getch();
    return 0;

}
void showAttributeUsage(int att)
{
    int n = 0, i = 0;
    while(n != '\0') {
        while(i != '\0') {
            cout << att[n][i] << " ";
            i++;

        }
        cout << endl;
        n++;
    }
}

Answer 1

我真的建议您使用std::vector：live example

void showAttributeUsage(const std::vector<std::vector<int>>& att)
{
    for (std::size_t n = 0; n != att.size(); ++n) {
        for (std::size_t i = 0; i != att.size(); ++i) {
            cout << att[n][i] << " ";
        }
        cout << endl;
    }
}

然后这样称呼：

showAttributeUsage(attVal);

Answer 2

查看您的代码，我认为没有理由不使用std::vector。

首先，您的代码使用非标准C ++扩展，即Variable Length Arrays（VLA）。如果您的目标是编写标准C ++代码，那么您编写的内容不是有效的标准C ++。

其次，您最初尝试传递int是错误的，但如果您使用vector，如果您使用{int，则传递vector的尝试看起来几乎相同1}}。

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>

typedef std::vector<int> IntArray;
typedef std::vector<IntArray> IntArray2D;

using namespace std;
void showAttributeUsage(const IntArray2D&);
int main()
{
   int qN, aN;
   cout << "Enter Number of Queries : ";
   cin >> qN;
   cout << "\nEnter Number of Attributes : ";
   cin >> aN;
   IntArray2D attVal(qN, IntArray(aN));
   //...  Input left out ...
   showAttributeUsage(attVal);
   return 0;
}

void showAttributeUsage(const IntArray2D& att)
{
   for_each(att.begin(), att.end(), 
            [](const IntArray& ia) {std::copy(ia.begin(), ia.end(), ostream_iterator<int>(cout, " ")); cout << endl;});
}

我省略了代码的输入部分。 vector使用[]就像常规数组一样，因此一旦声明了向量，就不必重写代码。您可以使用 molbdnilo 在其他答案中为您输入的代码来输入数据（不使用goto）。

其次，只是将其抛入混合，showAttributeUsage函数使用copy算法输出信息。 for_each抛出向量的每一行，为元素行调用std::copy。如果您使用的是兼容C ++ 11的编译器，则应编译以上内容。

Answer 3

你应该声明这样的函数。

void array_function(int m, int n, float a[m][n])
{
      for (int i = 0; i < m; i++)
          for (int j = 0; j < n; j++)
              a[i][j] = 0.0;
}

传递数组的维度。

Answer 4

这个问题已经回答here。您需要使用指针或模板。其他解决方案也存在。

总之做这样的事情：

template <size_t rows, size_t cols>
void showAttributeUsage(int (&array)[rows][cols])
{
    for (size_t i = 0; i < rows; ++i)
    {
        std::cout << i << ": ";
        for (size_t j = 0; j < cols; ++j)
            std::cout << array[i][j] << '\t';
        std::cout << std::endl;
    }
}

Answer 5

您正在使用编译器扩展，该扩展允许您声明在运行时确定大小的数组没有办法将具有此类维度的2D数组传递给函数，因为在编译时必须知道数组作为函数参数的所有维度。

您可以使用固定尺寸并使用读取的值作为传递给函数的限制：

const int max_queries = 100; 
const int max_attributes = 100;

void showAttributeUsage(int array[max_queries][max_attributes], int queries, int attributes);


int main()
{
    int attVal[max_queries][max_attributes];
    int qN = 0;
    int aN = 0;
    cout << "Enter Number of Queries (<= 100) : ";   
    cin >> qN;
    cout << "\nEnter Number of Attributes (<= 100) : ";   
    cin >> aN;

    cout << "\nEnter Attribute Usage Values" << endl;
    for (int n = 0; n < qN; n++)
    {
        cout << "\n\n***************** COLUMN " << n + 1 <<" *******************\n\n";
        for (int i = 0; i < aN; i++)
        {
            bool bad_input = true;
            while (bad_input)
            {
                bad_input = false;  // Assume that input will be correct this time.
                cout << "Use(Q" << n + 1 << " , " << "A" << i + 1 << ") = ";
                cin >> attVal[n][i];
                cout << endl;
                if (attVal[n][i] > 1 || attVal[n][i] < 0)
                { 
                    cout << "\n\nTHE VALUE MUST BE 1 or 0 . Please Re-Enter The Values\n\n";
                    bad_input = true;
                }
            }
        }
    }
    cout << "\n\nYOUR ATTRIBUTE USAGE MATRIX IS\n\n";
    showAttributeUsage(attVal, qN, aN);

    getch();
    return 0;   
}

void showAttributeUsage(int att[max_queries][max_attributes], int queries, int attributes)
{
    for (int i = 0; i < queries; i++)
    {
        for (int j = 0; j < attributes; j++)
        {
            cout << att[i][j] << " ";
        }
        cout << endl;
    }
}

为了比较，使用std::vector的相同程序，几乎相同但没有大小限制：

void showAttributeUsage(vector<vector<int> > att);

int main()
{
    cout << "Enter Number of Queries (<= 100) : ";   
    cin >> qN;
    cout << "\nEnter Number of Attributes (<= 100) : ";   
    cin >> aN;

    vector<vector<int> > attVal(qN, vector<int>(aN));

    cout << "\nEnter Attribute Usage Values"<<endl;
    for (int n = 0; n < qN; n++)
    {
        cout<<"\n\n***************** COLUMN "<<n+1<<" *******************\n\n";
        for (int i = 0; i < aN; i++)
        {
            bool bad = true;
            while (bad)
            {
                bad = false;
                cout << "Use(Q" << n + 1 << " , " << "A" << i + 1 << ") = ";
                cin >> attVal[n][i];
                cout << endl;
                if (attVal[n][i] > 1 || attVal[n][i] < 0)
                { 
                    cout << "\n\nTHE VALUE MUST BE 1 or 0 . Please Re-Enter The Values\n\n";
                    bad = true;
                }
            }
        }
    }
    cout << "\n\nYOUR ATTRIBUTE USAGE MATRIX IS\n\n";
    showAttributeUsage(attVal);

    getch();
    return 0;   
}

void showAttributeUsage(vector<vector<int> > att);
{
    for (int i = 0; i < att.size(); i++)
    {
        for (int j = 0; j < att[i].size(); j++)
        {
            cout << att[i][j] << " ";
        }
        cout << endl;
    }
}

Answer 6

特殊逻辑为我工作。终于找到了。： - ）

int** create2dArray(int rows, int cols) {

    int** array = new int*[rows];

    for (int row=0; row<rows; row++) {

        array[row] = new int[cols];

    }

    return array;

}



void delete2dArray(int **ar, int rows, int cols) {

    for (int row=0; row<rows; row++) {

        delete [] ar[row];

    }

    delete [] ar;

}


void loadDefault(int **ar, int rows, int cols) {

    int a = 0;

    for (int row=0; row<rows; row++) {

        for (int col=0; col<cols; col++) {

            ar[row][col] = a++;

        }

    }

}



void print(int **ar, int rows, int cols) {

    for (int row=0; row<rows; row++) {

        for (int col=0; col<cols; col++) {

            cout << " | " << ar[row][col];

        }

        cout << " | " << endl;

    }

}

int main () {

    int rows = 0;

    int cols = 0;

    cout<<"ENTER NUMBER OF ROWS:\t";cin>>rows;
    cout<<"\nENTER NUMBER OF COLUMNS:\t";cin>>cols;
    cout<<"\n\n";

    int** a = create2dArray(rows, cols);

    loadDefault(a, rows, cols);

    print(a, rows, cols);

    delete2dArray(a, rows, cols);
    getch();
    return 0;

}

Answer 7

如果使用的是c ++，则可以使用适用于任意尺寸的模板

template<typename T>
void func(T& v)
{
    // code here
}

int main()
{
    int arr[][7] = {
        {1,2,3,4,5,6,7},
        {1,2,3,4,5,6,7}
    };
    func(arr);
    char triplestring[][2][5] = {
        {
            "str1",
            "str2"
        },
        {
            "str3",
            "str4"
        }
    };
    func(triplestring);
    return 0;
}

将2D数组传递给c ++中的函数

7 个答案: