/* Program to demonstrate multidimensional arrays and pointers * as discussed in the thread: * * https://www.sololearn.com/Discuss/2376791/pointer-array-vs-multidimensional-array * */ #include #include using namespace std; void showarray(int arr[][10]); void showptrarray(int *arr[]); void showptrdata(int nrows, int ncols, int* ptr); void showptrptrdata(int nrows, int ncols, int ** pptr); int main(void) { int myarray[10][10]; // fixed 2D array int * ptrarray[10]; // array of pointers // fill the int array for (int i = 0; i < 10; i++) { for (int j = 0; j < 10; j++) { myarray[i][j] = i * 10 + j; } } // fill the *int array for (int i = 0; i < 10; i++) { // create the new int array (row) ptrarray[i] = new int[10]; } // show the size of the array myarray cout << "myarray " << sizeof(myarray) << endl; // now fill the multidimensional array for (int i = 0; i < 10; i++) { for (int j = 0; j < 10; j++) { ptrarray[i][j] = i * 10 + j; } } // show the size of the array ptrarray cout << "ptrarray " << sizeof(ptrarray) << endl; // display the contents of myarray cout << endl << "Contents of myarray in main" << endl; for (int i = 0; i < 10; i++) { for (int j = 0; j < 10; j++) { cout << setw(2) << setfill('0') << myarray[i][j] << " "; } cout << endl; } // display the contents of ptrarray cout << endl << "Contents of ptrarray in main" << endl; for (int i = 0; i < 10; i++) { for (int j = 0; j < 10; j++) { cout << setw(2) << setfill('0') << ptrarray[i][j] << " "; } cout << endl; } // display the array contents using a function showarray(myarray); // display the ptr array contents using a function showptrarray(ptrarray); // display array contents using a pointer to an int showptrdata(10, 10, (int *) myarray); // display array contents using a pointer to an int pointer showptrptrdata(10, 10, (int **) ptrarray); return 0; } void showarray(int arr[][10]) { // display the contents of an array cout << endl << "Contents of array in function" << endl; for (int i = 0; i < 10; i++) { for (int j = 0; j < 10; j++) { cout << setw(2) << setfill('0') << arr[i][j] << " "; } cout << endl; } } void showptrarray(int *arr[]) { // display the contents of an array of pointers cout << endl << "Contents of pointer array in function" << endl; for (int i = 0; i < 10; i++) { for (int j = 0; j < 10; j++) { cout << setw(2) << setfill('0') << *(arr[i] + j) << " "; } cout << endl; } } void showptrdata(int nrows, int ncols, int* ptr) { // display the data from an int pointer cout << endl << "Data from int pointer in function" << endl; for (int i = 0; i < nrows; i++) { for (int j = 0; j < ncols; j++) { cout << setw(2) << setfill('0') << *(ptr + (i * ncols) + j) << " "; } cout << endl; } } void showptrptrdata(int nrows, int ncols, int ** pptr) { // display the data from a pointer to an int pointer cout << endl << "Data from pointer to int pointer in function" << endl; for (int i = 0; i < nrows; i++) { for (int j = 0; j < ncols; j++) { cout << setw(2) << setfill('0') << *(*(pptr + i) + j) << " "; } cout << endl; } } /* The author of this work hereby waives all claim of copyright (economic and moral) * in this work and immediately places it in the public domain; it may be used, * distorted or destroyed in any manner whatsoever without further attribution or * notice to the creator. */

Pointers and Arrays