Fill an matrix with the following structure in c

问题

I have the following structures.

typedef struct arr_integer
{
  int size;
  int *arr;
}arr_arr_integer;

arr_arr_integer alloc_arr_integer(int len)
{
  arr_arr_integer a = {len, len > 0 ? malloc(sizeof(int) * len) : NULL};
  return a;
}

What I intend to do is fill the matrix with the above structures. But I don't know how to manipulate the structure to fill the matrix.

Tried it this way, but I get an error.

int main(int argc, char const *argv[])
{

  int len,rows,columns;

  scanf("%d",&rows);

  scanf("%d",&columns);

  len = rows * columns;

  arr_arr_integer Matrix = alloc_arr_integer(len);

  for (int i = 0; i < rows ; i++)
  {
    for (int j = 0; j < columns; j++)
    {
      scanf("%d",&Matrix.arr[i].arr[j]);
    }
  }

  return 0;
}

回答1:

Since you have a 2D matrix, it's much better/easier to store both dimensions in the matrix struct instead of the total (e.g. len).

And, it helps to have a function that returns a pointer to a given cell.

Here's a refactored version of your code.

I've generated two print functions that show a simple version and a somewhat faster version.

#include <stdio.h>
#include <stdlib.h>

typedef struct arr_integer {
    int ymax;
    int xmax;
    int *arr;
} arr_arr_integer;

arr_arr_integer
alloc_arr_integer(int ymax,int xmax)
{
    arr_arr_integer a;

    a.ymax = ymax;
    a.xmax = xmax;

    a.arr = malloc(ymax * xmax * sizeof(int));

    return a;
}

int *
mtxloc(arr_arr_integer *mtx,int y,int x)
{

    return &mtx->arr[(y * mtx->xmax) + x];
}

void
mtxprt(arr_arr_integer *mtx)
{

    for (int i = 0; i < mtx->ymax; i++) {
        for (int j = 0; j < mtx->xmax; j++) {
            int *ptr = mtxloc(mtx,i,j);
            printf(" [%d,%d]=%d",i,j,*ptr);
        }
        printf("\n");
    }
}

void
mtxprt2(arr_arr_integer *mtx)
{

    for (int i = 0; i < mtx->ymax; i++) {
        int *ptr = mtxloc(mtx,i,0);
        for (int j = 0; j < mtx->xmax; j++)
            printf(" [%d,%d]=%d",i,j,ptr[j]);
        printf("\n");
    }
}

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

    int len, rows, columns;

    scanf("%d", &rows);
    scanf("%d", &columns);

    arr_arr_integer Matrix = alloc_arr_integer(rows,columns);

    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < columns; j++) {
            int *ptr = mtxloc(&Matrix,i,j);
            scanf("%d", ptr);
        }
    }

    mtxprt(&Matrix);
    mtxprt2(&Matrix);

    return 0;
}

来源：https://stackoverflow.com/questions/63767458/fill-an-matrix-with-the-following-structure-in-c

标签

matrix

structure