Question

我试图理解点人。基本上,我试图把一个点子分配给另一个点,以便我获得两个层面的动态阵列。我可以要么把小oc用于分配*A,要么(假设我已经拥有一个阵列)A? 当我试图利用我双重分配的阵列获得A3.1[5]时,汇编者拒绝让我制定方案。我将如何建立这样一个两层分配阵列? 得到帮助。

#include <stdlib.h>
#include <stdio.h>
int main()
{
int *A;
A=(int *)malloc(sizeof(A)*100);
A[1]=(int *)malloc(sizeof(A[1])*100);
A[1][5]=10;//
printf("%d", (int)sizeof(A[1]));
free(A[1]);
free(A);
}

Answer 1

我怀疑你想要的确实是两维阵,而是一阵一阵阵。

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

int main()
{
   const int NUM_ROWS         = 100;
   const int NUM_INTS_PER_ROW = 200;

   // allocate a dynamic buffer of pointers; each pointer will
   // point to a 1D array of integers
   int ** rows = (int **) malloc(NUM_ROWS * sizeof(int *));

   // for each row, allocate the array of integers
   int i;
   for (i=0; i<NUM_ROWS; i++) rows[i] = (int *) malloc(NUM_INTS_PER_ROW * sizeof(int));

   // Populate the array
   for (i=0; i<NUM_ROWS; i++)
   {
      int j;
      for (j=0; j<NUM_INTS_PER_ROW; j++) rows[i][j] = 666;
   }

   // do stuff here...

   // Finally, free the data
   for (i=0; i<NUM_ROWS; i++) free(rows[i]);
   free(rows);

   return 0;
}

If you want a real 2D array (e.g. something that is laid out in a single contiguous block of memory, similar to int array[100][200], you re slightly out of luck, since C doesn t support dynamically-sized 2D arrays, but you can always fake it using a 1D array and a helper-function, like this:

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

// Returns a pointer to the item in the array at the given row and column
int * GetPointerToArrayItem(int * array, int numIntsPerRow, int row, int col)
{
   return array+(row*numIntsPerRow)+col;
}

int main()
{
   const int NUM_ROWS         = 100;
   const int NUM_INTS_PER_ROW = 200;

   int * array = (int *) malloc(NUM_ROWS * NUM_INTS_PER_ROW * sizeof(int));

   // Populate the array
   int i;
   for (i=0; i<NUM_ROWS; i++)
   {
      int j;
      for (j=0; j<NUM_INTS_PER_ROW; j++) 
      {
         *GetPointerToArrayItem(array, NUM_INTS_PER_ROW, i, j) = 666;
      }
   }

   // do stuff here...

   // Finally, free the data
   free(array);

   return 0;
}

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