Add suffix automaton

Author: YazanRi

String/String Automaton/suffix_automaton.cpp

@@ -0,0 +1,51 @@
+struct state
+{
+    int len, link;
+    map<char, int> next;
+};
+const int N = 300000 + 5;
+
+struct SA
+{
+    state st[2 * N];
+    int fpos[2 * N];
+    int sz, last;
+
+    void sa_init()
+    {
+        sz = last = 0;
+        st[0].len = 0;
+        st[0].link = -1;
+        ++sz;
+    }
+
+    void sa_extend(char c)
+    {
+        int cur = sz++;
+        st[cur].len = st[last].len + 1;
+        fpos[cur] = st[cur].len - 1;
+        int p;
+        for(p = last; p != -1 && !st[p].next.count(c); p = st[p].link)
+            st[p].next[c] = cur;
+        if(p == -1)
+            st[cur].link = 0;
+        else
+        {
+            int q = st[p].next[c];
+            if(st[p].len + 1 == st[q].len)
+                st[cur].link = q;
+            else
+            {
+                int clone = sz++;
+                st[clone].len = st[p].len + 1;
+                st[clone].next = st[q].next;
+                st[clone].link = st[q].link;
+                fpos[clone] = fpos[q];
+                for(; p != -1 && st[p].next[c] == q; p = st[p].link)
+                    st[p].next[c] = clone;
+                st[q].link = st[cur].link = clone;
+            }
+        }
+        last = cur;
+    }
+};