#include <iostream>
#include <vector>
#include <string>
#include <set>
#include <algorithm>
/*
This program finds the letters that appear in *every* word
from a given list. It uses idiomatic C++ and STL algorithms.
We break the logic into clean, reusable functions:
1. letters_of(word) → returns a set<char> of unique letters
2. intersect_sets(a, b) → returns intersection of two sets
3. common_letters(words) → returns letters common to all words
*/
// Convert a word into a set of its unique characters
std::set<char> letters_of(const std::string& word) {
return std::set<char>(word.begin(), word.end());
}
// Compute intersection of two sets using std::set_intersection
std::set<char> intersect_sets(const std::set<char>& a,
const std::set<char>& b) {
std::set<char> result;
std::set_intersection(
a.begin(), a.end(),
b.begin(), b.end(),
std::inserter(result, result.begin())
);
return result;
}
// Compute letters common to all words in the list
std::set<char> common_letters(const std::vector<std::string>& words) {
if (words.empty()) return {};
// Start with letters of the first word
std::set<char> common = letters_of(words[0]);
// Intersect with each subsequent word
for (size_t i = 1; i < words.size(); ++i) {
std::set<char> current = letters_of(words[i]);
common = intersect_sets(common, current);
}
return common;
}
int main() {
std::vector<std::string> words = {
"algebraic",
"alphabetic",
"ambiance",
"abacus",
"metabolic",
"parabolic",
"playback",
"drawback",
"fabricate",
"flashback",
"syllabic"
};
std::set<char> result = common_letters(words);
std::cout << "Common letters across all words:\n";
for (char c : result) {
std::cout << c << " ";
}
}
/*
run:
Common letters across all words:
a b c
*/
