Letter frequency

letterFrequency

using System;
using System.Collections.Generic; 
using System.IO;

namespace LetterFrequency
{
    public class Program
    {
        public static void Main(string[] args)
        {
            using(StreamReader sr = new StreamReader("letter_frequencies.in"))
            {
                string num = sr.ReadLine();
                int numberOfInputs = Int32.Parse(num);
                
                string line;
                int count = 1;
                
                while ((line = sr.ReadLine()) != null && 
                    (count <= numberOfInputs)) {
                                           
                    var sortedTuples = generateSortedTuples(line);
                                           
                    using (StreamWriter sw = File.AppendText("letter_frequencies.out")) {
                        sw.WriteLine("Case #{0}", count);
                     
                        foreach(var entry in sortedTuples) {
                            sw.WriteLine(String.Format("{0} {1}", entry.Ch, entry.Count));
                        }   
                    }
                    
                    count++;
                }
            }
            
            Console.WriteLine("Done");
        }
        
        static List<Tuple> generateSortedTuples(string s) {
            if (String.IsNullOrEmpty(s)) {
                return new List<Tuple>();
            }
            
            s = s.Replace(" ", "");
            
            var map = new Dictionary<char, int>();
            foreach(var ch in s) {
                if (map.ContainsKey(ch)) {
                    map[ch]++;
                } else {
                    map.Add(ch, 1);
                }
            }
            
            var allTuples = new List<Tuple>();
            foreach(var key in map.Keys) {
                allTuples.Add(new Tuple(key, map[key]));
            }
            
            allTuples.Sort();
            
            return allTuples;
        }
    }
    
    class Tuple : IComparable {
        public Tuple(char ch, int count) {
            Ch = ch;
            Count = count;
        }
        
        public char Ch { get; private set; }
        
        public int Count { get; private set; }
        
        public int CompareTo(Object other) {
            var otherTuple = other as Tuple;
            int result = otherTuple.Count.CompareTo(Count);
            if (result == 0) {
                return Ch.CompareTo(otherTuple.Ch);
            }
            
            return result;
        } 
        
    }
}