Question

我试图通过在我的程序2d-array中使用，将矩阵的零移位以获得其次要元素。如何正确删除（移位）二维数组的元素？

我知道如何通过排列其元素来处理一维数组

for (int i = DEL; i < (SIZE - 1); i++)
    array[i] = array[i + 1];

其中DEL-我们要删除的元素的索引，SIZE-数组的大小。但是多维数组的结果却不一样：

for (int i = DEL; i < (SIZE - 1); i++)
    for (int j = DEL; j < (SIZE - 1); j++)
        array[i][j] = array[i+1][j+1];

哪里有错误？

#include <iostream>

using namespace std;

int main()
{
    int array[3][3] = {
        1, 2, 3,
        4, 5, 6, 
        7, 8, 9};

    // Setting to zero 2nd row and 3rd column
    int m = 1; // 2
    int n = 2; // 3


    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            array[m][j] = 0;
            array[i][n] = 0;
            cout << array[i][j];
            // Trying to shift every element, which equals zero
            if (array[i][j] == 0)
                for (int k = i; k < 2; k++)
                    for (int l = j; l < 2; l++)
                        array[k][l] = array[k+1][l+1];          

        }
        cout << endl;
    }



    cout << endl;

    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
            cout << array[i][j];
        cout << endl;
    }
}

我得到：

但是实际上我希望最后的输出是这样的：

120
780
000

Answer 1

我认为“排列”一词在这里不合适。您要从二维数组中删除行和列。

但是您犯了一些语义错误。我已为您修复此问题，并在下面显示了更正的代码。

一个大建议。尝试将一个大问题缩小为几个小问题。您在多嵌套循环中尝试过多。一个接一个地做。

请参阅：

#include <iostream>

constexpr size_t MaxArraySize = 3;

int main()
{
    int array[MaxArraySize][MaxArraySize] = {
        1, 2, 3,
        4, 5, 6,
        7, 8, 9 };

    // Setting to zero 2nd row and 3rd column
    int rowToDelete = 1; // 2
    int colToDelete = 2; // 3

    // Set cell to delete to 0
    for (int row = 0; row < MaxArraySize; ++row)
    {
        for (int col = 0; col < MaxArraySize; ++col)
        {
            array[rowToDelete][col] = 0;
            array[row][colToDelete] = 0;
            std::cout << array[row][col];
        }
        std::cout << '\n';
    }

    // First shift all rows
    for (int row = rowToDelete; row < MaxArraySize - 1; ++row)
        for (int col = 0; col < MaxArraySize; ++col)
            array[row][col] = array[row+1][col];

    // Then shift all cols
    for (int col = colToDelete; col < MaxArraySize-1; ++col)
        for (int row = 0; row < MaxArraySize; ++row)
            array[row][col] = array[row][col+1];

    // Set the cells that were shifted away to 0
    for (int row = 0; row < MaxArraySize; ++row)
        array[row][MaxArraySize - 1] = 0;
    for (int col = 0; col < MaxArraySize; ++col)
        array[MaxArraySize - 1][col] = 0;

    // Show result
    std::cout << "\n\nResult\n\n";
    for (int row = 0; row < MaxArraySize; ++row)
    {
        for (int col = 0; col < MaxArraySize; ++col)
            std::cout << array[row][col];
        std::cout << '\n';
    }
}

第二甚至更重要。您正在使用带有纯C样式数组的纯C代码。您代码中唯一的C ++使用的是iostream。那不是很好。

尝试使用C ++。永远不要使用纯C样式数组。尝试使用STL中的算法和容器。为变量使用更好的名称。

生成的代码片段将非常简单。在这里，我们实际上是删除行和列。请参阅：

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

int main()
{
    // Lambda for printing the matric to std::cout
    auto print = [](std::vector<std::vector<int>> & m) {
        std::for_each(m.begin(), m.end(), [](std::vector<int> & vi) { std::copy(vi.begin(), vi.end(), std::ostream_iterator<int>(std::cout, " ")); std::cout << '\n'; });
    };
    // You can add whatever values. 
    std::vector<std::vector<int>> matrix {
        {11, 12, 13, 14},
        {15, 16, 17, 18},
        {19, 20, 21, 22},
        {23, 24, 25, 26}
    };
    // Show initial data
    std::cout << "\n\nInitial matrix:\n";
    print(matrix);

    constexpr size_t RowToDelete = 1; // Row 2
    constexpr size_t ColToDelete = 2; // Column3

    // Erase row
    matrix.erase(matrix.begin() + RowToDelete);
    // Erase column in each row
    std::for_each(matrix.begin(),matrix.end(), [ColToDelete](std::vector<int> & vi) { vi.erase(vi.begin() + ColToDelete); });

    // Show result
    std::cout << "\n\nResulting matrix with deleted row " << RowToDelete+1 << " and deleted column " << ColToDelete+1 << '\n';
    print(matrix);

    return 0;
}

希望这会有所帮助。。

置换2D数组中的元素

1 个答案: