c - 线性存储器中的二维数组

Question

我在结构中创建二维数组时遇到问题。到目前为止，这是我的代码，但我确定它是错误的数组存储在结构中的 char 指针中，但数组必须用于 float ，所以这也让我感到困惑:

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

#define MAX_ROWS 5000
#define MAX_COLUMNS 5000

struct array
{
        int rows;
        int columns;
        int order;
        char *base_pointer; /* pointer to array of bytes. In this array, float numbers will be stored (4 bytes each) */
};
 struct array* initialize(int rows, int columns, int order)
 {

  /* Allocate the required memory for the 2D array to store float values (Ex: 1.45) with "rows" and "columns" */
  struct array* array = (struct array*)malloc(rows * columns);
  /* Make sure the size is within 1 to MAX_ROWS and 1 to MAX_COLUMNS specified in main.c. If not return null pointer */
  array->rows = rows;
  array->columns = columns;
  array->order = order;
  /* Initialize the 2D array to the all zeroes (0.0) */
  /* Assign suitable values to all the elements of the structure and return the struct pointer */
  return array;
 }

Answer 1

我想这就是您要找的:

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

#define MAX_ROWS 5000
#define MAX_COLUMNS 5000

struct array
{
        int rows;
        int columns;
        int order;
        char *base_pointer; /* pointer to array of bytes. In this array, float numbers will be stored (4 bytes each) */
};
struct array* initialize(int rows, int columns, int order)
{
  int i,
      size = columns * rows * sizeof(float);
  /* Allocate the required memory for the 2D array to store float values (Ex: 1.45) with "rows" and "columns" */

  // If you want to allocate both the structure and the internal storage in one malloc:
  /*
  struct array* array = (struct array*) malloc(sizeof(struct array) + size);
  array->base_pointer = &((char*)array)[sizeof(struct array)];
  */

  struct array* array = malloc(sizeof(struct array));
  if(!array) {
    return 0; // error
  }
  array->base_pointer = malloc(size);
  if(!array->base_pointer) {
    return 0; // error
  }

  for(i = 0; i < size; i++) {
    array->base_pointer[i] = 0;
  }
  /* Make sure the size is within 1 to MAX_ROWS and 1 to MAX_COLUMNS specified in main.c. If not return null pointer */
  array->rows = rows;
  array->columns = columns;
  array->order = order;
  /* Initialize the 2D array to the all zeroes (0.0) */
  /* Assign suitable values to all the elements of the structure and return the struct pointer */
  return array;
 }

 void insert(struct array* arr, int row, int column, float value) {
    float* floatArr = (float*)arr->base_pointer;
    floatArr[(column * arr->rows) + row] = value;
 }

 float retrieve(struct array* arr, int row, int column) {
    float* floatArr = (float*)arr->base_pointer;
    return floatArr[(column * arr->rows) + row];
 }

您正在为内部数组分配所需的内存，并试图将其用于结构。相反，您需要为该结构分配内存，然后为其内部数组 base_pointer 提供指向单独分配的指针。