// https://leetcode.com/problems/longest-word-in-dictionary
class Solution {
public:
string longestWord(vector<string>& words) {
unordered_set<string> s;
for (const auto& w : words) s.insert(w);
string best = "";
for (const auto& w : words) {
if (w.size() < best.size() or (w.size() == best.size() and best < w))
continue;
for (int i = 1, L = w.size(); i <= L; ++i)
if (!s.count(w.substr(0, i))) goto BPP;
best = w;
BPP:;
}
return best;
}
};