Question

I’ve read lots of posts about sorting a 2D array but I still can’t master it so I was wondering if anyone can offer me some advice…

I have an aray which lists letters and quantity (I’m doing a frequency anaysis on a piece of text). I’ve read this data into a rectangle array and need to order it by highest frequency first. Here’s my code so far:

    //create 2D array to contain ascii code and quantities
    int[,] letterFrequency = new int[26, 2];

    //fill in 2D array with ascaii code and quantities
    while (asciiNo <= 90)
     {

       while ((encryptedText.Length - 1) > counter)
      {
                if (asciiNo == (int)encryptedText[index])
               {
                      letterCount++;
               }
                counter++;
                index++;
      }

    letterFrequency[(storeCount), (0)] = (char)(storeCount+66);
    letterFrequency[(storeCount), (1)] = letterCount;
    storeCount++;
    counter=0;
    index=0;
    letterCount = 0;
    asciiNo++;
    }

Answer 1

You are using a 2D array to represent 2 separate vectors – the symbols and the counts. Instead, use 2 separate arrays. Array.Sort has an overload that takes 2 arrays, and sorts on one array, but applies the changes to both, achieving what you want.

This would also allow you to use a char[] for the characters rather than int[]:

char[] symbols = ...
int[] counts = ...
...load the data...
Array.Sort(counts, symbols);
// all done!

At this
point, the counts have been ordered, and the symbols will still match index-by-index with the count they relate to.