// Pair structure: (letter, frequency)
interface Pair {
letter: string;
freq: number;
}
// sortByFrequency — counts how often each letter appears and returns a sorted list
function sortByFrequency(text: string): Pair[] {
// Create a frequency array for 26 lowercase letters, initialized to 0
const freq: number[] = Array(26).fill(0);
// Iterate through the string and count only alphabetic characters
for (const ch of text) {
if (/[a-zA-Z]/.test(ch)) {
const lower: string = ch.toLowerCase();
const index: number = lower.charCodeAt(0) - "a".charCodeAt(0);
freq[index]++;
}
}
// Build an array of (letter, frequency) pairs
const result: Pair[] = [];
for (let i = 0; i < 26; i++) {
const letter: string = String.fromCharCode("a".charCodeAt(0) + i);
result.push({ letter, freq: freq[i] });
}
// Sort pairs by frequency in descending order
result.sort((a: Pair, b: Pair) => b.freq - a.freq);
return result;
}
// Build a string sorted by frequency: ddddddddddddccccccbbbbbaaaafffeehhgs
function buildSortedString(sorted: Pair[]): string {
let output: string = "";
for (const p of sorted) {
// append 'p.letter' repeated p.freq times
if (p.freq > 0) {
output += p.letter.repeat(p.freq);
}
}
return output;
}
// Main logic
function main(): void {
// Input text to analyze
const text: string = "bbcabddddccafffadbbcdccsedddddhhgade";
// Get sorted frequency list
const sorted: Pair[] = sortByFrequency(text);
// Print each letter and its frequency
for (const p of sorted) {
if (p.freq !== 0) {
console.log(`${p.letter}: ${p.freq}`);
}
}
// Print the reconstructed sorted string
const lettersSortedByFrequency: string = buildSortedString(sorted);
console.log("\nSorted string:", lettersSortedByFrequency);
}
main();
/*
run:
d: 12
c: 6
b: 5
a: 4
f: 3
e: 2
h: 2
g: 1
s: 1
Sorted string: ddddddddddddccccccbbbbbaaaafffeehhgs
*/
