Count occurrences of number in array C#

April 15, 2024

I have an array moviesRented with the following values stored in it:
17 3 3 2 2 2 1 1 1 1. The values were read from parsed data in a txt file

I need to print out the count of each value. For example the output should be:
4 occurrence of 1
3 occurrence of 2
2 occurrence of 3
1 occurrence of 17

Here is my current code:

            StreamReader inFile = new StreamReader("project-files/transactions.txt");
            string line = inFile.ReadLine();

            while(line != null){

                string[] temp = line.Split("#");
            
                moviesRented[count] = int.Parse(temp[2]);                
                count++;

                line = inFile.ReadLine();
            }

            inFile.Close();

            for(int i = 0; i < count - 1; i++){
                for(int j = i + 1; j < count; j++){

                    if(moviesRented[i] < moviesRented[j]){
                        int temp = moviesRented[i];
                        moviesRented[i] = moviesRented[j];
                        moviesRented[j] = temp;
                    }
                }
            }

            // output sorted array
            for(int i = 0; i < count; i++){
                Console.WriteLine(moviesRented[i]);
            }

I’m able to get the needed values from the text file (they are stored in the moviesRented array) and I also sorted them from highest to lowest.

Here is the moviesRented output after the sort:
17
3
3
2
2
2
1
1
1
1

How would I go about counting the values? I tried something like this:

        StreamReader inFile = new StreamReader("project-files/transactions.txt");
        string line = inFile.ReadLine();

        while(line != null){

            string[] temp = line.Split("#");
        
            moviesRented[count] = int.Parse(temp[2]);                
            count++;

            line = inFile.ReadLine();
        }

        inFile.Close();

        for(int i = 0; i < count - 1; i++){

            int tempCount = 0;
            for(int j = i + 1; j < count; j++){

                if(moviesRented[i] < moviesRented[j]){
                    int temp = moviesRented[i];
                    moviesRented[i] = moviesRented[j];
                    moviesRented[j] = temp;
                }

                // this is new compared to the code above
                // it compares iteration with next iteration
                // and if they match then add 1 to tempCount
                if(moviesRented[i] == moviesRented[j]){
                    tempCount++;
                }
            }
            Console.WriteLine($"{moviesRented[i]} {tempCount}");
        }

Which counts it, but there are too many instances of each value – here is the output with the code above:
17 1
3 1
3 2
2 2
2 1
2 3
1 3
1 2
1 1

But I need the HIGHEST occurrence value of each word – not all of them like in the output above.

How would I go about displaying (printing to console) each moviesRented value and how many times it occurs in descending order such as the first output I mentioned above:

4 occurrence of 1
3 occurrence of 2
2 occurrence of 3
1 occurrence of 17

>Solution :

The easiest way is to use LINQ:

var statistics = from x in moviesRented
                 group x by x into g
                 select new { Number = g.Key, Count = g.Count() };

foreach(var statItem in statistics)
   Console.WriteLine($"{statItem.Count} occurence(s) of {statItem.Number}");

The well-known classic algorithm is to use dictionary (hashtable), which contains incremented count of each value.