From b4bf3abf5f1d74a6659abd5c056c4f4e3eb9b897 Mon Sep 17 00:00:00 2001
From: jurajsic <juraj.sic@outlook.com>
Date: Wed, 20 Sep 2023 14:01:32 +0200
Subject: [PATCH] optimization

---
 include/mata/nfa/strings.hh | 2 +-
 src/strings/nfa-strings.cc  | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/mata/nfa/strings.hh b/include/mata/nfa/strings.hh
index a66b28936..3739f80d0 100644
--- a/include/mata/nfa/strings.hh
+++ b/include/mata/nfa/strings.hh
@@ -116,7 +116,7 @@ std::set<Word> get_shortest_words(const Nfa& nfa);
 /**
  * @brief Get all the one symbol words accepted by @p nfa.
  */
-std::set<mata::Symbol> get_accepted_symbols(const Nfa& nfa);
+std::set<Symbol> get_accepted_symbols(const Nfa& nfa);
 
 /**
  * @brief Get the lengths of all words in the automaton @p aut. The function returns a set of pairs <u,v> where for each
diff --git a/src/strings/nfa-strings.cc b/src/strings/nfa-strings.cc
index a5a7aabf8..9d6cf43ea 100644
--- a/src/strings/nfa-strings.cc
+++ b/src/strings/nfa-strings.cc
@@ -148,8 +148,10 @@ std::set<mata::Symbol> mata::strings::get_accepted_symbols(const Nfa& nfa) {
     std::set<mata::Symbol> accepted_symbols;
     for (State init : nfa.initial) {
         for (const SymbolPost& symbol_post_init : nfa.delta[init]) {
-            if (!accepted_symbols.contains(symbol_post_init.symbol) && nfa.final.intersects_with(symbol_post_init.targets)) {
-                accepted_symbols.insert(symbol_post_init.symbol);
+            mata::Symbol sym = symbol_post_init.symbol;
+            auto symbol_it = accepted_symbols.lower_bound(sym);
+            if (*symbol_it != sym && nfa.final.intersects_with(symbol_post_init.targets)) {
+                accepted_symbols.insert(symbol_it, sym);
             }
         }
     }