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source/String/AhoCorasick.cpp

@@ -0,0 +1,49 @@
+struct Node {
+    int next[26]; int par, int fail; bool isfin = false;
+    Node(){fail = 0; fors(i, 0, 25) next[i] = -1;}
+};
+Node trie[N]; int c;
+void insert(char s[], int i, int node) {
+    if(s[i] == '\0') {
+        trie[node].isfin = true; return;
+    }
+    if(trie[node].next[s[i]-'a'] == -1) {
+        trie[node].next[s[i]-'a'] = ++c;
+        trie[c].par = node;
+    }
+    insert(s, i+1, trie[node].next[s[i]-'a']);
+}
+void bfs() {
+    queue<pii> q; q.push({0, -1});
+    while(!q.empty()) {
+        auto [node, x] = q.front(); q.pop();
+        if(x != -1) {
+            int pf = trie[trie[node].par].fail;
+            while(pf != 0 and trie[pf].next[x] == -1) pf = trie[pf].fail;
+
+            if(trie[node].par != 0 and trie[pf].next[x] != -1)
+            {
+                trie[node].fail = trie[pf].next[x];
+                trie[node].isfin |= trie[trie[pf].next[x]].isfin;
+            }
+            else trie[node].fail = 0;
+        }
+        fors(i, 0, 25) {
+            if(trie[node].next[i] == -1) continue;
+            q.push({trie[node].next[s[i]-'a'], i});
+        }
+    }
+}
+
+// For char* s, insert(s+1, 0, 0);
+// trie[0].fail = 0; bfs();
+// find trie from s:
+int now = 0, ok = false;
+for(int i = 0; s[i]; i++) {
+    while(now != 0 and trie[now].next[s[i]-'a'] == -1) now = trie[now].fail;
+
+    if(trie[now].next[s[i]-'a'] != -1) {
+        now = trie[now].next[s[i]-'a'];
+        if(trie[now].isfin) ok = true;
+    }
+}