diff --git a/src/regexp.rs b/src/regexp.rs
--- a/src/regexp.rs
+++ b/src/regexp.rs
@@ -1,13 +1,14 @@
-use std::collections::{HashMap, HashSet, VecDeque};
+use std::{collections::{HashMap, HashSet, VecDeque}, iter};
 
 mod token;
 pub use token::ParsingError;
 use token::parse;
 
-const START: i32 = -1;
-const FAIL: i32 = -2;
+const START_NFA: usize = usize::MAX;
+const START_DFA: usize = 0;
+const FAIL: usize = usize::MAX>>1;
 
-fn encode_set(set: &HashSet<i32>) -> String {
+fn encode_set(set: &HashSet<usize>) -> String {
 	let mut v = Vec::from_iter(set.iter());
 	v.sort();
 	let res: Vec<String> = v.into_iter().map(|x| x.to_string()).collect();
@@ -16,44 +17,51 @@ fn encode_set(set: &HashSet<i32>) -> Str
 
 #[derive(Debug)]
 pub struct Regexp {
-	rules: HashMap<(i32, char), HashSet<i32>>,
-	end_states: HashSet<i32>
+	rules: HashMap<(usize, char), HashSet<usize>>,
+	end_states: HashSet<usize>,
+	alphabet: Vec<char>
 }
 
 impl Regexp {
 	pub fn new(pattern: &String) -> Result<Regexp, ParsingError> {
 		let r = parse(pattern, 0)?;
 		let pattern_chars = Vec::from_iter(pattern.chars());
-		let mut rules: HashMap<(i32, char), HashSet<i32>> = HashMap::new();
+		let mut rules: HashMap<(usize, char), HashSet<usize>> = HashMap::new();
+		let mut alphabet: HashSet<char> = HashSet::new();
 		
 		for i in r.list_first() {
 			let c = pattern_chars[i];
-			let key = (START, c);
+			alphabet.insert(c);
+			let key = (START_NFA, c);
 			match rules.get_mut(&key) {
-				Some(set) => {set.insert(i as i32);},
-				None => {rules.insert(key, HashSet::from([i as i32]));}
+				Some(set) => {set.insert(i);},
+				None => {rules.insert(key, HashSet::from([i]));}
 			};
 		}
 
 		for (i, j) in r.list_neighbours() {
 			let c = pattern_chars[j];
-			let key = (i as i32, c);
+			alphabet.insert(c);
+			let key = (i, c);
 			match rules.get_mut(&key) {
-				Some(set) => {set.insert(j as i32);},
-				None => {rules.insert(key, HashSet::from([j as i32]));}
+				Some(set) => {set.insert(j);},
+				None => {rules.insert(key, HashSet::from([j]));}
 			};
 		}
 
-		let mut end_states = HashSet::from_iter(r.list_last().into_iter().map(|i| i as i32));
+		let mut end_states = HashSet::from_iter(r.list_last().into_iter());
 		if r.is_skippable() {
-			end_states.insert(START);
+			end_states.insert(START_NFA);
 		}
 
-		return Ok(Regexp{rules, end_states});
+		let mut alphabet_vec = Vec::from_iter(alphabet.into_iter());
+		alphabet_vec.sort();
+
+		return Ok(Regexp{rules, end_states, alphabet: alphabet_vec});
 	}
 
 	pub fn eval(&self, s: String) -> bool {
-		let mut multistate = HashSet::from([START]);
+		let mut multistate = HashSet::from([START_NFA]);
 
 		for c in s.chars() {
 			let mut new_multistate = HashSet::new();
@@ -72,18 +80,22 @@ impl Regexp {
 	}
 
 	pub fn determinize(&self) -> RegexpDFA {
-		let mut rules: HashMap<(i32, char), i32> = HashMap::new();
-		let mut end_states: HashSet<i32> = HashSet::new();
-		if self.end_states.contains(&START) {end_states.insert(START);}
+		let alphabet_index: HashMap<char, usize> = self.alphabet.iter().enumerate().map(|(i, c)| (*c, i)).collect();
+		let n = alphabet_index.len();
+		let mut compact_rules = vec![FAIL; n];
+		let mut end_states: HashSet<usize> = HashSet::new();
+		if self.end_states.contains(&START_NFA) {end_states.insert(START_DFA);}
 
-		let mut index_new = HashMap::from([(START.to_string(), START)]);
-		let mut index_multi = HashMap::from([(START.to_string(), HashSet::from([START]))]);
-		let mut stack = Vec::from([START.to_string()]);
+		// string hash -> single int DFA state
+		let mut index_new = HashMap::from([(START_NFA.to_string(), START_DFA)]);
+		// string hash -> HashSet NFA multistate
+		let mut index_multi = HashMap::from([(START_NFA.to_string(), HashSet::from([START_NFA]))]);
+		let mut stack = Vec::from([START_NFA.to_string()]);
 
 		while !stack.is_empty() {
 			let state_hash = stack.pop().unwrap();
 			let multistate = &index_multi[&state_hash];
-			let mut new_rules: HashMap<char, HashSet<i32>> = HashMap::new();
+			let mut new_rules: HashMap<char, HashSet<usize>> = HashMap::new();
 
 			for key in self.rules.keys().filter(|key| multistate.contains(&key.0)) {
 				let (_st, c) = key;
@@ -99,79 +111,90 @@ impl Regexp {
 				let target_hash = encode_set(&target_set);
 				let is_end = target_set.iter().any(|st| self.end_states.contains(st));
 				if !index_new.contains_key(&target_hash) {
-					let target_new = index_new.len() as i32;
+					let target_new = index_new.len();
 					index_new.insert(target_hash.clone(), target_new);
 					index_multi.insert(target_hash.clone(), target_set);
+					compact_rules.extend(iter::repeat(FAIL).take(n));
 					stack.push(target_hash.clone());
 				}
-				rules.insert((index_new[&state_hash], c), index_new[&target_hash]);
+				compact_rules[index_new[&state_hash]*n + alphabet_index[&c]] = index_new[&target_hash];
 				if is_end {
 					end_states.insert(index_new[&target_hash]);
 				}
 			}
 		}
 
-		return RegexpDFA{rules, end_states};
+		return RegexpDFA{rules: compact_rules, end_states, alphabet_index};
 	}
 }
 
 pub struct RegexpDFA {
-	rules: HashMap<(i32, char), i32>,
-	end_states: HashSet<i32>
+	rules: Vec<usize>,
+	end_states: HashSet<usize>,
+	alphabet_index: HashMap<char, usize>
 }
 
 impl RegexpDFA {
 	pub fn eval(&self, s: String) -> bool {
-		let mut state = START;
+		let n = self.alphabet_index.len();
+		let mut state = START_DFA;
 
 		for c in s.chars() {
-			if let Some(x) = self.rules.get(&(state, c)) {
-				state = *x;
+			if let Some(ci) = self.alphabet_index.get(&c) {
+				state = self.rules[state*n + ci];
 			} else {
 				return false;
 			}
+			if state == FAIL {
+				return false;
+			}
 		}
 
 		return self.end_states.contains(&state);
 	}
 
 	pub fn reduce(&self) -> RegexpDFA {
+		if self.alphabet_index.len() == 0 {
+			return RegexpDFA{rules: self.rules.clone(), end_states: self.end_states.clone(), alphabet_index: self.alphabet_index.clone()};
+		}
 		let equivalents = self.find_equivalent_states();
 		return self.collapse_states(equivalents);
 	}
 
 	pub fn normalize(&self) -> RegexpDFA {
-		let mut index = HashMap::from([(START, START)]);
-		let mut queue = VecDeque::from([START]);
+		let n = self.alphabet_index.len();
+		if n == 0 {
+			return RegexpDFA{rules: self.rules.clone(), end_states: self.end_states.clone(), alphabet_index: self.alphabet_index.clone()}; 
+		}
+		let m = self.rules.len()/n;
+		let mut index: Vec<usize> = vec![FAIL;m];
+		index[0] = 0;
+		let mut queue = VecDeque::from([START_DFA]);
+
+		let mut rules = vec![];
+		let mut k = 1;
 
 		while !queue.is_empty() {
-			let state = queue.pop_front().unwrap();
-			let mut edges: Vec<((i32, char), i32)> = self.rules.iter()
-				.filter(|((st, c), t)| *st == state)
-				.map(|((st, c), t)| ((*st, *c), *t)).collect();
-			edges.sort();
-			for ((_st, _c), t) in edges {
-				if !index.contains_key(&t) {
-					index.insert(t, index.len() as i32);
-					queue.push_back(t);
+			let si = queue.pop_front().unwrap();
+			let row = &self.rules[si*n..(si+1)*n];
+			for &sj in row {
+				if sj != FAIL && index[sj] == FAIL {
+					index[sj] = k;
+					k += 1;
+					queue.push_back(sj);
 				}
 			}
+			rules.extend(row.iter().map(|&st| if st != FAIL {index[st]} else {FAIL}));
 		}
 
-		let rules = self.rules.iter().map(|((st, c), t)| ((index[st], *c), index[t])).collect();
-		let end_states = self.end_states.iter().map(|st| index[st]).collect();
+		let end_states = self.end_states.iter().map(|st| index[*st]).collect();
 		
-		return RegexpDFA{rules, end_states};
+		return RegexpDFA{rules, end_states, alphabet_index: self.alphabet_index.clone()};
 	}
 
-	fn find_equivalent_states(&self) -> Vec<(i32, i32)> {
-		let state_set: HashSet<i32> = HashSet::from_iter(self.rules.values().copied());
-		let mut state_vec: Vec<i32> = Vec::from_iter(state_set.into_iter());
-		state_vec.push(START);
-		state_vec.push(FAIL);
-		state_vec.sort();
-		let alphabet: HashSet<char> = self.rules.keys().map(|(_st, c)| c).copied().collect();
-
+	fn find_equivalent_states(&self) -> Vec<(usize, usize)> {
+		let n = self.alphabet_index.len();
+		let state_vec: Vec<usize> = (0..self.rules.len()/n).collect();
 		let mut equivalents = HashSet::new();
 		state_vec.iter().enumerate().for_each(|(i, s1)| {
 			equivalents.extend(
@@ -181,14 +204,14 @@ impl RegexpDFA {
 			);
 		});
 
-		let mut n = usize::MAX;
-		while equivalents.len() < n {
-			n = equivalents.len();
+		let mut m = usize::MAX;
+		while equivalents.len() < m {
+			m = equivalents.len();
 			equivalents = equivalents.iter().filter(|(s1, s2)| {
-				!alphabet.iter().any(|c| {
-					let t1 = self.rules.get(&(*s1, *c)).unwrap_or(&FAIL);
-					let t2 = self.rules.get(&(*s2, *c)).unwrap_or(&FAIL);
-					let key = (*t1.min(t2), *t1.max(t2));
+				!(0..n).any(|ci| {
+					let t1 = self.rules[s1*n + ci];
+					let t2 = self.rules[s2*n + ci];
+					let key = (t1.min(t2), t2.max(t1));
 					return t1 != t2 && !equivalents.contains(&key);
 				})
 			}).copied().collect();
@@ -197,18 +220,31 @@ impl RegexpDFA {
 		return Vec::from_iter(equivalents.into_iter());
 	}
 
-	fn collapse_states(&self, mut equivalents: Vec<(i32, i32)>) -> RegexpDFA {
-		let mut rules = self.rules.clone();
-		let mut end_states = self.end_states.clone();
-		equivalents.sort();
+	fn collapse_states(&self, equivalents: Vec<(usize, usize)>) -> RegexpDFA {
+		let n = self.alphabet_index.len();
+		let m = self.rules.len()/n;
+		let mut rules = Vec::new();
 
+		let mut eq_mapping: Vec<usize> = ((0..m)).collect();
 		for (s1, s2) in equivalents.into_iter() {
-			rules = rules.into_iter()
-				.filter(|((st, _c), _t)| *st != s2)
-				.map(|(key, t)| (key, if t==s2 {s1} else {t})).collect();
-			end_states.remove(&s2);
+			eq_mapping[s2] = eq_mapping[s2].min(s1);
 		}
 
-		return RegexpDFA{rules, end_states};
+		let mut discard_mapping: Vec<usize> = ((0..m)).collect();
+		let mut discard_count = 0;
+
+		for si in 0..m {
+			if eq_mapping[si] != si {
+				discard_count += 1;
+				continue;
+			}
+			discard_mapping[si] = si-discard_count;
+			rules.extend(self.rules[si*n..(si+1)*n].iter().map(|&st| if st!=FAIL {eq_mapping[st]} else {FAIL}));
+		}
+
+		rules = rules.into_iter().map(|st| if st!=FAIL {discard_mapping[st]} else {FAIL}).collect();
+		let end_states = self.end_states.iter().map(|st| discard_mapping[eq_mapping[*st]]).collect();
+
+		return RegexpDFA{rules, end_states, alphabet_index: self.alphabet_index.clone()};
 	}
 }