C# 2D Array calling it another class through obj.method();

Question

Write a Java class that has a static method named count that accepts a 2D-Array of integers and a target integer value as parameters and returns the number of occurrences of the target value in the array. For example, if a variable named list refers to an array containing values {{3,5,7,94}{5,6,3,50}} then the call of count(list, 3) should return 2 because there are 2 occurrences of the value 3 in the array.

Here is my coding and it's not giving me proper output P.S :-I have been told to take count method as public not static

class java
{
    public int count(int [,] list,int n)
    {
        int c = 0;
        for (int i = 0; i <list.Length; i++)
        {
            for (int j = 0; j < list.Length; j++)
            {
                if (list[i, j] == n)
                {
                    c++;
                }
            }
        }
        return c;
    }

class Program
{
    static void Main(string[] args)
    {
        java jv = new java();
        int[,] arr = { { 3, 5, 7, 94 }, {5, 6, 3, 50 } };
        int k=0;
        jv.count(arr,k);
    }
}

yeah i tried debugging it. on if(list[i,j]==n) it says index out of range — M Saad, Sep 19 '15 at 09:09
I've added an answer which allows you to get rid of the entire loop, might make your code a little bit cleaner. — Tamir Vered, Sep 19 '15 at 09:51
What is even going on here? Is it C# or Java? Why have you called your class "java", with a missing uppercase letter? — user9993, Sep 19 '15 at 10:40
@user9993 It's C# :) probably lecturer forgot to change it to c# so i took it as "class java" — M Saad, Sep 20 '15 at 18:48

score 2 · Answer 1 · edited May 23 '17 at 12:24

Iterating Multi-Dimensional arrays requires you to iterate each dimension with it's own Length, which means i and j should be 0-3 and 0-1 respectively.

as can be seen in the picture but for a different dimensioned array:

GetLength(0) would return 4.

GetLength(1) would return 3.

What you are doing is iterating them when i = (0 to Length) over j = (0 to Length) when Length = Height * Width = 8 in your case which means 8 over 8.

So your count() method should look like that:

public int count(int[,] list,int n)
{
    int c = 0;
    for (int i = 0; i < list.GetLength(0); i++)
    {
        for (int j = 0; j < list.GetLength(1); j++)
        {
            if (list[i, j] == n)
            {
                c++;
            }
        }
    }
    return c;
}

if you would like to iterate the array as an array of arrays instead of getting things complicated with "Which dimension am I iterating now?" you can use Jagged Arrays (Of course there are more things to consider about it), this will allow you to replace the whole method with this one short Linq:

public int count(int[][] list,int n)
{
    return list.SelectMany(x => x).Count(x => x == n);
}

or:

public int count(int[][] list, int n)
{
    return list.Sum(x => x.Count(y => y == n));
}

Roman Dibikhin · Answer 2 · 2015-09-19T09:40:52.797

1

Note the i against j in inner for. And do use i <list.GetLength(0) and j < list.GetLength(1) against list.Length

class java
{
    public int count(int [,] list,int n)
    {
        int c = 0;
        for (int i = 0; i < list.GetLength(0); i++)
        {
            for (int j = 0; j < list.GetLength(1); j++)
            {
                if (list[i, j] == n)
                {
                    c++;
                }
            }
        }
        return c;
    }

class Program
{
    static void Main(string[] args)
    {
        java jv = new java();
        int[,] arr = { {3,5,7,94 }, {5,6,3,50 } };
        int k=5;
        Console.WriteLine(jv.count(arr,k));
    }
}

edited Sep 19 '15 at 09:40

answered Sep 19 '15 at 09:01

Roman Dibikhin

856
4
15

You beat me by a few seconds! – EvilTak Sep 19 '15 at 09:02
It's an accident. Have luck and have fun;) – Roman Dibikhin Sep 19 '15 at 09:04
@MSaad Use `int k=5;`. – Roman Dibikhin Sep 19 '15 at 09:25
@MSaad And use `Console.WriteLine(jv.count(arr,k));` – Roman Dibikhin Sep 19 '15 at 09:27
@MSaad do understand your errors and try to avoid them next time :) – Roman Dibikhin Sep 19 '15 at 09:48

Fabjan · Answer 3 · 2015-09-19T15:06:40.780

Since Array has implemented IEnumerable you can simply use foreach loop here (feel free to change static to instance method) :

    public static int count(int[,] list, int n)
    {
        int c = 0;
        foreach (var item in list) if (item == n) c++;
        return c;
    }

Usage:

  static void Main()
    {
        var r = count(new int[,]{
            {
                5, 8, 7, 8
            }, 
            {
                0, 8, 9, 3
            }}, 8);

        Console.WriteLine(r);

output : 3

P.S. Generally if possible, it is best to use a for loop as it is faster than foreach but in these case i like that if you use foreach you don't have nested for loops nor GetLength(x) calls it's just one line of code and it has almost same performance...

EvilTak · Answer 4 · 2018-01-01T06:32:31.260

-1

Your error is in this line:

for (int j = 0; i < list.Length; j++)

It should be

for (int j = 0; j < list.Length; j++)

edited Jan 01 '18 at 06:32

answered Sep 19 '15 at 09:02

EvilTak

7,091
27
36

Are you storing the returned value anywhere? If you aren't then there's no use is there? – EvilTak Sep 19 '15 at 09:12
i am returning value to c "return c;" – M Saad Sep 19 '15 at 09:25
No I mean are you storing the returned value? For example `int i = jv.count(arr, k)`. And k = 0, which isn't present in your array. – EvilTak Sep 19 '15 at 09:29

C# 2D Array calling it another class through obj.method();

4 Answers4