homework/2darray.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3
   4 /* Incorrect  */
   5 void foo1(int **mat, int rows, int cols)
   6 {
   7     int i, j;
   8
   9     for (i = 0; i < rows; i++) {
  10         for (j = 0; j < cols; j++)
  11             printf("%d ", mat[i][j]);
  12         printf("\n");
  13     }
  14 }
  15
  16 /* Correct */
  17 void foo2(int **mat, int rows, int cols)
  18 {
  19     int i, j;
  20     int **aux;
  21
  22     aux = malloc(rows * sizeof(int *));
  23     if (aux == NULL) {
  24         perror("malloc");
  25         exit(EXIT_FAILURE);
  26     }
  27
  28     for (i = 0; i < rows; i++) {
  29         aux[i] = (int *)mat + cols * i;
  30         for (j = 0; j < cols; j++)
  31             printf("%d ", aux[i][j]);
  32         printf("\n");
  33     }
  34
  35     free(aux);
  36 }
  37
  38 /* Correct */
  39 void foo3(int **mat, int rows, int cols)
  40 {
  41     int i, j;
  42
  43     for (i = 0; i < rows; i++) {
  44         for (j = 0; j < cols; j++)
  45             printf("%d ", *((int *)mat + cols * i) + j);
  46         printf("\n");
  47     }
  48 }
  49
  50 int main(void)
  51 {
  52     int mat[4][3] = { { 1,  2,  3},
  53                       { 4,  5,  6},
  54                       { 7,  8,  9},
  55                       {10, 11, 12} };
  56
  57     foo3((int **)&mat[0][0], 4, 3);
  58     foo2((int **)&mat[0][0], 4, 3);
  59     /* foo1((int **)&mat[0][0], 4, 3); */
  60
  61     return EXIT_SUCCESS;
  62 }