P3808 【模板】AC 自动机（简单版）

https://www.luogu.com.cn/record/87931577

Luogu/P3808/P3808.cpp

@@ -0,0 +1,134 @@
+#include <iostream>
+#include <queue>
+#include <string>
+#include <unordered_map>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+class AcAutomaton {
+  private:
+    struct node {
+        int cnt;
+        node *child[26], *fail;
+
+        node()
+            : cnt(0), fail(nullptr) {
+            std::fill_n(child, 26, nullptr);
+        }
+
+        ~node() {
+            for (int i = 0; i < 26; i++) {
+                if (child[i] != nullptr) {
+                    delete child[i];
+                }
+            }
+        }
+    };
+
+    node* root;
+
+  public:
+    AcAutomaton()
+        : root(new node()) {}
+
+    ~AcAutomaton() {
+        delete root;
+    }
+
+    void insert(std::string s) {
+        node* cur = root;
+
+        for (char c : s) {
+            if (cur->child[c - 'a'] == nullptr) {
+                cur->child[c - 'a'] = new node();
+            }
+
+            cur = cur->child[c - 'a'];
+        }
+
+        cur->cnt++;
+    }
+
+    void build() {
+        std::queue<node*> q;
+
+        for (int i = 0; i < 26; i++) {
+            if (root->child[i] != nullptr) {
+                q.push(root->child[i]);
+                root->child[i]->fail = root;
+            }
+        }
+
+        while (!q.empty()) {
+            auto cur = q.front();
+            q.pop();
+
+            for (int i = 0; i < 26; i++) {
+                if (cur->child[i] == nullptr) continue;
+
+                auto p = cur->fail;
+
+                while (p != nullptr) {
+                    if (p->child[i] != nullptr) {
+                        cur->child[i]->fail = p->child[i];
+
+                        break;
+                    }
+
+                    p = p->fail;
+                }
+
+                if (p == nullptr) cur->child[i]->fail = root;
+
+                q.push(cur->child[i]);
+            }
+        }
+    }
+
+    int query(std::string t) {
+        int res = 0;
+        node* cur = root;
+
+        for (char c : t) {
+            while (cur != root && cur->child[c - 'a'] == nullptr) cur = cur->fail;
+            cur = cur->child[c - 'a'] == nullptr ? root : cur->child[c - 'a'];
+
+            node* p = cur;
+
+            while (p != root && p->cnt >= 0) {
+                res += p->cnt;
+                p->cnt = -1;
+                p = p->fail;
+            }
+        }
+
+        return res;
+    }
+};
+
+int n;
+std::string s, t;
+AcAutomaton ac;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> s;
+
+        ac.insert(s);
+    }
+
+    ac.build();
+
+    cin >> t;
+
+    cout << ac.query(t) << endl;
+
+    return 0;
+}