C++ Week 13 Multi-dimensional Arrays

[robcat2075]

Multi-dimensional arrays let you store tables of date. Nested loops make it easy to populate and output these tables.

 

John Purcell suggests a multiplication table exercise.

In addition to outputting the whole table, choose a few random array elements and output their values.

The output will look like this. Format your output neatly!

 

Mult Table!

1       2       3       4       5       6       7       8       9       10
2       4       6       8       10      12      14      16      18      20
3       6       9       12      15      18      21      24      27      30
4       8       12      16      20      24      28      32      36      40
5       10      15      20      25      30      35      40      45      50
6       12      18      24      30      36      42      48      54      60
7       14      21      28      35      42      49      56      63      70
8       16      24      32      40      48      56      64      72      80
9       18      27      36      45      54      63      72      81      90
10      20      30      40      50      60      70      80      90      100

table value at index 5,3: 24
table value at index 3,9: 40

 

 

 

[robcat2075]

@Rodney @Roger @Shelton

I was quite mistaken last night about array declarations. The extra braces don't matter! At least not for our simple integer arrays.

This sample program shows four different styles all producing the same result...

// MultiDDeclareTest.cpp : program to declare multi-dimensional arrays
// and access a value in them

#include <iostream>
using namespace std;

int main()
{
    //simplest declaration...
    int tableA[3][4] = { 1,2,3,4,2,4,6,8,3,6,9,12 };

    //line breaks added for readability...
    int tableB[3][4] = { 
        1,2,3,4,
        2,4,6,8,
        3,6,9,12 };

    //extra braces added for readability
    int tableC[3][4] = { {1,2,3,4},{2,4,6,8},{3,6,9,12} };

    //line breaks and braces added for readability
    int tableD[3][4] = { 
        {1,2,3,4},
        {2,4,6,8},
        {3,6,9,12} };

    // remember that array elements are numbered starting with zero...
    cout << "tableA[1][3] = " << tableA[1][3] << endl;
    cout << "tableB[1][3] = " << tableB[1][3] << endl;
    cout << "tableC[1][3] = " << tableC[1][3] << endl;
    cout << "tableD[1][3] = " << tableD[1][3] << endl;

}

 

Output...

tableA[1][3] = 8
tableB[1][3] = 8
tableC[1][3] = 8
tableD[1][3] = 8