Question

我的朋友们，我在这里结束了。

此函数的目的是获取指向2D数组，行号和列大小的指针，并返回指向2D数组中指定值行的地址。我不知道怎么做到这一点，有什么建议吗？

提前致谢。

double* get_row(double *the_array, int row_num, int col_size) {
cout << "Get Row : "<< the_array[row_num]<< "\n";
return the_array+row_num;}

cout的原因是确认它是正确的值集我正在返回一个指针，但我不确定我是否正确实现了它。

编辑：

这是完整的代码

#include "TwoDArray.h"

using namespace std;

/*
 * 
 */

void set_row(double *the_array, int row_num, int col_size, double *row_vals) {
    for (int i = 0; i < col_size; i++)
        the_array[i] = *row_vals + i;
    cout << "Set Row:"<< *the_array << "\n";
}

double get_element(double *the_array, int row_num, int col_size, int col_num) {
    double thisElement = (*(the_array + (row_num * col_size)) + col_num);
    return thisElement;
}

double* get_row(double *the_array, int row_num, int col_size) {
    cout << "Get Row : "<< the_array[row_num]<< "\n";
    return the_array+row_num;
}

double sum(double *the_array, int row_size, int col_size) {

    double sum = 0.0;
    for (int j = 0; j < row_size; j++) {
        for (int i = 0; i < col_size * row_size; i++) {
            sum += the_array[i] + j;

        }
        return sum;
    }
}

double find_max(double *the_array, int row_size, int col_size) {
    double max_so_far = the_array[0];
    for (int j = 0; j < row_size; j++)
        for (int i = 0; i < col_size * row_size; i++)
            if (the_array[i] + j > max_so_far)
                max_so_far = the_array[i] + j;
    return max_so_far - 1;
}

double find_min(double *the_array, int row_size, int col_size) {
    double min_so_far = the_array[0];
    for (int j = 0; j < row_size; j++)
        for (int i = 0; i < col_size * row_size; i++)
            if (the_array[i] + j < min_so_far)
                min_so_far = the_array[i] + j;
    return min_so_far;


}

int main(int argc, char** argv) {

    const int row_size = 2; //i
    const int col_size = 3; //j
    double B[2][3] = {
        {68, 2, 44},
        {7, 8, 3}
    };
    double (*p)[3] = B;
    double C[2][3] = {
        {1, 1, 1},
        {1, 2, 3}};

    double (*f)[3] = C;

    cout << "\n" << "Sum of all Elements = " << sum(*p, 2, 3) << "\n"; ///Expected: 132
    cout << "\n" << "Get Element = " << get_element(*p, 1, 0, 0) << "\n"; //Expected: 68
    cout << "\n" << "Largest Element = " << find_max(*p, 2, 3) << "\n"; //Expected: 68
    cout << "\n" << "Smallest Element = " << find_min(*p, 2, 3) << "\n"; //Expected: 2
    cout << "\n" << "Get Row = " << get_row(*p, 0, col_size) << "\n"; //Expected: 2
    set_row(*p, 2, 3, *f);
    cout << "\n" << B[2][3];
    cout << "\n";



}

Answer 1

当x + y * col_size和x是二维数组坐标时，

y会给出数组的一维索引。因此，要访问行的第一个元素，您需要设置x = 0和y = row_num。而不仅仅是返回元素的地址。

return &the_array[row_num * col_size];

Answer 2

我有一些类似的代码，我一直在使用矩阵的一维表示，也许这会有所帮助

// 2D to 1D
int get_index(int x, int y)
{
    return y*WIDTH + x;
}

// 1D to 2D
int get_x(int index) { index % WIDTH; }
int get_y(int index) { index / WIDTH; }

函数将地址返回到2D数组中的一行值？

2 个答案: