How to check how many times a value appears in an array?

Question

So this is what I want my output to look like:

How many numbers? 10
Give number 1: 1
Give number 2: 3
Give number 3: 1
Give number 4: 3
Give number 5: 4
Give number 6: 6
Give number 7: 4
Give number 8: 8
Give number 9: 2
Give number 10: 1
Number 1 appeared 3 times
Number 2 appeared 1 times
Number 3 appeared 2 times
Number 4 appeared 2 times
Number 6 appeared 1 times
Number 8 appeared 1 times

The thing is, I've got the part which reads the user input done. However, I have no idea how to continue with the part which tells how many times each number appeared.

Also, I'm doing this as a schoolwork so most of the code is in Finnish. I hope you can still understand it, though.

using System;

namespace Ohjelma
{
    class Ohjelma
    {
        static void Main()
        {
            Console.Write("Kuinka monta lukua? ");
            int pituus = Convert.ToInt32(Console.ReadLine());

            int[] luvut = new int[pituus];


            for (int i = 0; i < pituus; i++)
            {
                Console.Write("Anna {0}. luku:", i + 1);
                luvut[i] = Convert.ToInt32(Console.ReadLine());
            }

            for (int i = 0; i < luvut.Length; i++)
            {
                Console.Write(luvut[i]);

            }
            Console.ReadLine();
        }
    }
}

Edit: Sorry about the code block on the example of what it should output, not exactly sure how to use blockquotes even though I tried. Thanks!

Perhaps it would help if you wrote out the steps in English (or Finnnish - I just mean "not code") and then see which of those steps you're having trouble writing the code for. — Pete Baughman, Apr 10 '14 at 17:52
Possible duplicate of [A method to count occurrences in a list](https://stackoverflow.com/questions/1139181/a-method-to-count-occurrences-in-a-list) — Liam, Nov 03 '17 at 08:54

score 7 · Answer 1 · answered Apr 10 '14 at 17:51

You can use LINQ like:

var query = luvut.GroupBy(r => r)
                .Select(grp => new
                {
                    Value = grp.Key,
                    Count = grp.Count()
                });

For output you can use:

foreach (var item in query)
{
    Console.WriteLine("Value: {0}, Count: {1}", item.Value, item.Count);
}

user3437460 · Accepted Answer · 2017-11-03T10:06:36.713

int[] num = { 1, 1, 1, 3, 3, 4, 5, 6, 7, 0 };
int[] count = new int[10];

//Loop through 0-9 and count the occurances
for (int x = 0; x < 10; x++){
    for (int y = 0; y < num.Length; y++){
        if (num[y] == x)
            count[x]++;
    }
}

//For displaying output only            
for (int x = 0; x < 10; x++)
    Console.WriteLine("Number " + x + " appears " + count[x] + " times");

Program Output:

Number 0 appears 1 times
Number 1 appears 3 times
Number 2 appears 0 times
Number 3 appears 2 times
Number 4 appears 1 times
Number 5 appears 1 times
Number 6 appears 1 times
Number 7 appears 1 times
Number 8 appears 0 times

I understand how bad it feels when all your classmates had finish theirs, and you are still struggling. My codes should be simple enough for your learning.

With minimum changes you can make this to work for C# as well. Question is tagged with C# not Java. — Habib, Apr 10 '14 at 17:58

score 0 · Answer 3 · edited Nov 03 '17 at 09:34

If you don't want to use LINQ, you can code as follows:-

public class Program 
{
   public static void Main()
   {
       int[] arr1 = new int[] {1,3,3,5,5,4,1,2,3,4,5,5,5};

       List<int> listArr1 = arr1.ToList();

       Dictionary<int,int> dict1 = new Dictionary<int,int>();

       foreach(int i in listArr1)
       {
          if(dict1.ContainsKey(i))
          {
              int value  = dict1[i];
              value++;
              dict1[i]= value;
          }
          else
          {
              dict1.Add(i,1);
          }
       }

       for(int x = 0 ; x < dict1.Count(); x++)
       {        
          Console.WriteLine("Value {0} is repeated {1} times", dict1.Keys.ElementAt(x),dict1[dict1.Keys.ElementAt(x)]);                       
       }
   }
}

How to check how many times a value appears in an array?

3 Answers3

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