better automaton + eertree

Author: imirdy

content/string/eertree.cpp

@@ -0,0 +1,36 @@
+constexpr int ALPHABET_SIZE = 26;
+constexpr char OFFSET = 'a';
+struct Eertree {
+	struct State {
+		int len, link = 0, par;
+		array<int, ALPHABET_SIZE> nxt;
+
+		State(int l, int p) : len(l), par(p) {nxt.fill(-1);}
+	};
+
+	vector<State> st = {State(-1, -1), State(0, -1)};
+	vector<int> s = {-1};
+	int cur = 0;
+	Eertree(string& t) {
+		st.reserve(sz(t) + 2);
+		for (auto c : t) extend(c - OFFSET);
+	};
+
+	int getLink(int u) {
+		while (s.end()[-st[u].len - 2] != s.back()) u = st[u].link;
+		return u;
+	}
+
+	void extend(int c) {
+		s.push_back(c);
+		int old = cur = getLink(cur);
+		if (st[cur].nxt[c] == -1) {
+			st[cur].nxt[c] = sz(st);
+			st.emplace_back(st[cur].len + 2, cur);
+
+			cur = getLink(st[cur].link);
+			st.back().link = min(cur + 1, old) ? st[cur].nxt[c] : 1;
+		}
+		cur = st[old].nxt[c];
+	}
+};

content/string/string.tex

@@ -127,6 +127,6 @@ \section{Strings}
 	\sourcecode{string/suffixAutomaton.cpp}
 \end{algorithm}
 
-\begin{algorithm}{Trie}
-	\sourcecode{string/trie.cpp}
+\begin{algorithm}{Eertree}
+	\sourcecode{string/eertree.cpp}
 \end{algorithm}

content/string/suffixAutomaton.cpp

@@ -2,9 +2,10 @@ constexpr int ALPHABET_SIZE = 26;
 constexpr char OFFSET = 'a';
 struct SuffixAutomaton {
 	struct State {
-		int len, link = -1;
+		int len, firstPos, link = -1;
+		bool clone = false;
 		array<int, ALPHABET_SIZE> nxt; // map if large Alphabet
-		State(int l) : len(l) {fill(all(nxt), -1);}
+		State(int l) : len(l), firstPos(l) {fill(all(nxt), -1);}
 	};
 
 	vector<State> st = {State(0)};
@@ -29,9 +30,9 @@ struct SuffixAutomaton {
 			if (st[p].len + 1 == st[q].len) {
 				st[cur].link = q;
 			} else {
-				st.emplace_back(st[p].len + 1);
-				st.back().link = st[q].link;
-				st.back().nxt = st[q].nxt;
+				st.emplace_back(st[q]);
+				st.back().len = st[p].len + 1;
+				st.back().clone = true;
 				for (; p != -1 && st[p].nxt[c] == q; p = st[p].link) {
 					st[p].nxt[c] = sz(st) - 1;
 				}