improved suffix automaton

2 files changed, 37 insertions, 48 deletions

diff --git a/string/suffixAutomaton.cpp b/string/suffixAutomaton.cpp
index c6205da..8b79822 100644
--- a/string/suffixAutomaton.cpp
+++ b/string/suffixAutomaton.cpp
@@ -1,70 +1,59 @@
-constexpr char MIN_CHAR = 'a';
-constexpr ll ALPHABET_SIZE = 26;
+constexpr int ALPHABET_SIZE = 26;
+constexpr char OFFSET = 'a';
 struct SuffixAutomaton {
 	struct State {
-		int length, link;
-		vector<int> next;
-		State() : next(ALPHABET_SIZE) {}
+		int len, link = -1;
+		int nxt[ALPHABET_SIZE] = {}; // map if large Alphabet
+		State(int l) : len(l) {}
 	};
-	vector<State> states;
-	int size, last;
 
-	SuffixAutomaton(const string &s) : states(2*sz(s)) {
-		size = 1; last = 0;
-		states[0].link = -1;
-		for (auto c : s) extend(c - MIN_CHAR);
+	vector<State> st{0};
+	int last = 0;
+
+	SuffixAutomaton(const string &s) {
+		st.reserve(2 * sz(s));
+		for (auto c : s) extend(c - OFFSET);
 	}
 
 	void extend(int c) {
-		int current = size++;
-		states[current].length = states[last].length + 1;
-		int pos = last;
-		while (pos != -1 && !states[pos].next[c]) {
-			states[pos].next[c] = current;
-			pos = states[pos].link;
+		st.emplace_back(st[last].len + 1);
+		int p = last, cur = last = sz(st) - 1;
+		for (; p != -1 && !st[p].nxt[c]; p = st[p].link) {
+			st[p].nxt[c] = cur;
 		}
-		if (pos == -1) states[current].link = 0;
+		if (p == -1) st[cur].link = 0;
 		else {
-			int q = states[pos].next[c];
-			if (states[pos].length + 1 == states[q].length) {
-				states[current].link = q;
+			int q = st[p].nxt[c];
+			if (st[p].len + 1 == st[q].len) {
+				st[cur].link = q;
 			} else {
-				int clone = size++;
-				states[clone].length = states[pos].length + 1;
-				states[clone].link = states[q].link;
-				states[clone].next = states[q].next;
-				while (pos != -1 && states[pos].next[c] == q) {
-					states[pos].next[c] = clone;
-					pos = states[pos].link;
+				st.emplace_back(st[p].len + 1);
+				st.back().link = st[q].link;
+				copy(all(st[q].nxt), st.back().nxt); // back.nxt=[q].nxt
+				for (; p != -1 && st[p].nxt[c] == q; p = st[p].link) {
+					st[p].nxt[c] = sz(st) - 1;
 				}
-				states[q].link = states[current].link = clone;
+				st[q].link = st[cur].link = sz(st) - 1;
 		}}
-		last = current;
+	}
+
+	vector<int> calculateTerminals() {
+		vector<int> terminals;
+		for (int p = last; p != -1; p = st[p].link) {
+			terminals.push_back(p);
+		}
+		return terminals;
 	}
 
 	// Pair with start index (in t) and length of LCS.
 	pair<int, int> longestCommonSubstring(const string &t) {
 		int v = 0, l = 0, best = 0, bestpos = 0;
 		for (int i = 0; i < sz(t); i++) {
-			int c = t[i] - MIN_CHAR;
-			while (v && !states[v].next[c]) {
-				v = states[v].link;
-				l = states[v].length;
-			}
-			if (states[v].next[c]) {v = states[v].next[c]; l++;}
-			if (l > best) {best = l; bestpos = i;}
+			int c = t[i] - OFFSET;
+			for (; v && !st[v].nxt[c]; v = st[v].link) l = st[v].len;
+			if (st[v].nxt[c]) v = st[v].nxt[c], l++;
+			if (l > best) best = l, bestpos = i;
 		}
 		return {bestpos - best + 1, best};
 	}
-
-	// Returns all terminals of the automaton.
-	vector<int> calculateTerminals() {
-		vector<int> terminals;
-		int pos = last;
-		while (pos != -1) {
-			terminals.push_back(pos);
-			pos = states[pos].link;
-		}
-		return terminals;
-	}
 };
diff --git a/tcr.pdf b/tcr.pdf
index 2b8297e..e18fce8 100644
--- a/tcr.pdf
+++ b/tcr.pdf