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Write C code to dynamically allocate one, two and three dimensional arrays (using malloc())
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Its pretty simple to do this in the C language if you know how to use C pointers. Here are some example C code snipptes....
One dimensional array
int *myarray = malloc(no_of_elements * sizeof(int));
//Access elements as myarray[i]
Two dimensional array
Method1
int **myarray = (int **)malloc(no_of_rows * sizeof(int *));
for(i = 0; i < no_of_rows; i++)
{
myarray[i] = malloc(no_of_columns * sizeof(int));
}
// Access elements as myarray[i][j]
Method2 (keep the array's contents contiguous)
int **myarray = (int **)malloc(no_of_rows * sizeof(int *));
myarray[0] = malloc(no_of_rows * no_of_columns * sizeof(int));
for(i = 1; i < no_of_rows; i++)
myarray[i] = myarray[0] + (i * no_of_columns);
// Access elements as myarray[i][j]
Method3
int *myarray = malloc(no_of_rows * no_of_columns * sizeof(int));
// Access elements using myarray[i * no_of_columns + j].
Three dimensional array
#define MAXX 3
#define MAXY 4
#define MAXZ 5
main()
{
int ***p,i,j;
p=(int ***) malloc(MAXX * sizeof(int ***));
for(i=0;i<MAXX;i++)
{
p[i]=(int **)malloc(MAXY * sizeof(int *));
for(j=0;j<MAXY;j++)
p[i][j]=(int *)malloc(MAXZ * sizeof(int));
}
for(k=0;k<MAXZ;k++)
for(i=0;i<MAXX;i++)
for(j=0;j<MAXY;j++)
p[i][j][k]=<something>;
}
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Last updated:
November 3, 2005
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