#include <iostream>
#include <vector>
#include <algorithm>
#include <cctype>
// sortByFrequency — counts how often each letter appears and returns a sorted list
std::vector<std::pair<char,int>> sortByFrequency(const std::string &s) {
std::vector<int> freq(26, 0);
for (char c : s) {
if (isalpha(c)) {
freq[tolower(c) - 'a']++;
}
}
std::vector<std::pair<char,int>> result;
for (int i = 0; i < 26; i++) {
result.push_back({char('a' + i), freq[i]});
}
sort(result.begin(), result.end(),
[](auto &a, auto &b) { return a.second > b.second; });
return result;
}
// Build a string sorted by frequency: ddddddddddddccccccbbbbbaaaafffeehhgs
std::string buildSortedString(const std::vector<std::pair<char,int>> &sorted) {
std::string out;
for (auto &p : sorted) {
out.append(p.second, p.first); // append 'p.first' repeated p.second times
}
return out;
}
int main() {
std::string text = "bbcabddddccafffadbbcdccsedddddhhgade";
auto sorted = sortByFrequency(text);
// Print each letter and its frequency
for (auto &p : sorted) {
if (p.second != 0)
std::cout << p.first << ": " << p.second << std::endl;
}
// Print the reconstructed sorted string
std::string letters_sorted_by_frequency = buildSortedString(sorted);
std::cout << "\nSorted string: " << letters_sorted_by_frequency << std::endl;
}
/*
run:
d: 12
c: 6
b: 5
a: 4
f: 3
e: 2
h: 2
g: 1
s: 1
Sorted string: ddddddddddddccccccbbbbbaaaafffeehhgs
*/
