using System;
using System.Collections.Generic;
using System.Text;
class LetterFrequency
{
// Pair structure: (letter, frequency)
struct Pair
{
public char Letter;
public int Freq;
public Pair(char letter, int freq) {
Letter = letter;
Freq = freq;
}
}
// sortByFrequency — counts how often each letter appears and returns a sorted list
static List<Pair> SortByFrequency(string s)
{
int[] freq = new int[26]; // frequency array for 26 lowercase letters
// Iterate through the string and count only alphabetic characters
foreach (char c in s) {
if (char.IsLetter(c)) {
freq[char.ToLower(c) - 'a']++;
}
}
// Build a list of (letter, frequency) pairs
List<Pair> result = new List<Pair>();
for (int i = 0; i < 26; i++) {
result.Add(new Pair((char)('a' + i), freq[i]));
}
// Sort pairs by frequency in descending order
result.Sort((a, b) => b.Freq.CompareTo(a.Freq));
return result;
}
// Build a string sorted by frequency: ddddddddddddccccccbbbbbaaaafffeehhgs
static string BuildSortedString(List<Pair> sorted)
{
StringBuilder outStr = new StringBuilder();
foreach (Pair p in sorted) {
// append 'p.Letter' repeated p.Freq times
if (p.Freq > 0) {
outStr.Append(new string(p.Letter, p.Freq));
}
}
return outStr.ToString();
}
static void Main()
{
// Input text to analyze
string text = "bbcabddddccafffadbbcdccsedddddhhgade";
// Get sorted frequency list
List<Pair> sorted = SortByFrequency(text);
// Print each letter and its frequency
foreach (Pair p in sorted) {
if (p.Freq != 0)
Console.WriteLine($"{p.Letter}: {p.Freq}");
}
// Print the reconstructed sorted string
string lettersSortedByFrequency = BuildSortedString(sorted);
Console.WriteLine();
Console.WriteLine("Sorted string: " + lettersSortedByFrequency);
}
}
/*
run:
d: 12
c: 6
b: 5
a: 4
f: 3
e: 2
h: 2
g: 1
s: 1
Sorted string: ddddddddddddccccccbbbbbaaaafffeehhgs
*/
