CSIS113A

Lecture 11

Multi-dimensional Arrays

Glenn Stevenson CSIS 113A MSJC

Multi-dimensional Intro

• Arrays can come in just about as many dimensions as you would like. – My opinion is that if you have to go more than two

dimensions, there may be a better way of doing things.

• Think of a two dimension array as a grid or kind of like a bingo card that consists of rows and columns.– Like the old Battleship game– You declare a two dimensional array the same way

you would a one dimensional array except that you have to add another set of brackets:

Glenn Stevenson CSIS 113A MSJC

2D Array Depicted

Glenn Stevenson CSIS 113A MSJC

Rows & Columns

• Think of the number in the first bracket as the number of rows and the number in the second bracket as the number of columns.

Glenn Stevenson CSIS 113A MSJC

2D Arays & Memory

• In memory, the elements are contiguous, like this:

Glenn Stevenson CSIS 113A MSJC

2D Array Initialization

Glenn Stevenson CSIS 113A MSJC

Rules To Live By• You must supply the number of columns (the

second subscript). • The two dimensional array must be enclosed in

curly braces • Te closing curly brace surrounding the array

must have a semicolon • Each row is surrounded by curly braces • Each value within the row must be comma

separated • All rows are comma separated

Glenn Stevenson CSIS 113A MSJC

Storage & Retrieval

Glenn Stevenson CSIS 113A MSJC

Glenn Stevenson CSIS 113A MSJC

#include <iostream>#include <ctime>using namespace std;int main(){int ar[5][5];

srand(time(0));   for(int row = 0; row < 5; row++)   {      for(int col = 0; col < 5; col++)      {         ar[row][col] = rand() % 101;      }   }

   for(int row = 0; row < 5; row++)   {      for(int col = 0; col < 5; col++)      {         cout << ar[row][col] << "\t";      }      cout << endl;   }

   return 0;}

Multi-Dimensional Arrays As Arguments

Glenn Stevenson CSIS 113A MSJC

• Passing 2D arrays to functions is a little different than passing single dimension arrays but, not much.

• When you call the function you still just pass the array name, and you are still passing the base memory address of the array (address of first element or array[0])

Example

Glenn Stevenson CSIS 113A MSJC

Glenn Stevenson CSIS 113A MSJC

#include <iostream>#include <ctime> using namespace std;void fillArray(int ar[][5], int numRows);void printArray(const int ar[][5], int size);int main(){int array[5][5];

   fillArray(array, 5);   printArray(array, 5);

return 0;}void fillArray(int ar[][5], int numRows){   srand(time(0));   for(int row = 0; row < numRows; row++)   {      for(int col = 0; col < 5; col++)      {         ar[row][col] = rand() % 101;      }   }}

Glenn Stevenson CSIS 113A MSJC

void printArray(const int ar[][5], int numRows){   for(int row = 0; row < numRows; row++)   {      for(int col = 0; col < 5; col++)      {         cout << ar[row][col] << "\t";      }      cout << endl;   }}