Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

C# C# Collections Arrays Jagged Arrays

helpme

what should go to in the part where it isdeclaring 2 dimension array? I get compiler error

Math.cs
using System;
namespace Treehouse.CodeChallenges
{
    public static class MathHelpers
    {
        public static int[][] BuildMultiplicationTable(int maxFactor)
        {
           Array[][] array = new Array[maxFactor][];
            for(int i=0; i<=maxFactor; i++)
            {
                for(int j=0; j<=maxFactor; j++)
                {
                    array[i][j] = i*j;
                }
            }
        }
    }
}

2 Answers

Steven Parker
Steven Parker
229,968 Points

Here's a few hints:

  • the array size must be larger than the highest index used
  • each row must be separately initialized
  • the function must return the completed table
namespace Treehouse.CodeChallenges
{
    public static class MathHelpers
    {
        public static int[][] BuildMultiplicationTable(int maxFactor)
        {
            int[][] sheet = new int[maxFactor+1][];

            for(int i=0; i<=maxFactor; i++)
            {
                for(int j=0; j<=maxFactor; j++)
                {
                     sheet[i][j] = i*j;

                }
            }
            return sheet;
        }
    }
}

how about this i got error "Object reference not set to an instance of an object"

Steven Parker
Steven Parker
229,968 Points

It looks like you implemented 2 of my 3 hints, but you still need to initialize each row by creating an array for the 2nd dimension.

You might want to take another look at the Jagged Arrays video, particularly around 4:40 where the rows are created.