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P3808 【模板】AC 自动机（简单版）

Browse Source 
https://www.luogu.com.cn/record/103489926
This commit is contained in:
Baoshuo Ren 2023-03-03 11:00:06 +08:00
parent 37cb0c04e9
commit 7cd4ddfcee
Signed by: baoshuo
GPG Key ID: 00CB9680AB29F51A
1 changed files with 42 additions and 18 deletions
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60
Luogu/P3808/P3808.cpp
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@ -11,29 +11,32 @@ class AcAutomaton {
private: private:
struct node { struct node {
int cnt; int cnt;
std::shared_ptr<node> child[26], fail; std::weak_ptr<node> child[26], fail;
node() node()
: cnt(0), fail(nullptr) { : cnt(0), fail() {}
std::fill(std::begin(child), std::end(child), nullptr);
}
}; };
std::shared_ptr<node> root; std::shared_ptr<node> root;
std::vector<std::shared_ptr<node>> nodes;
public: public:
AcAutomaton() AcAutomaton()
: root(new node()) {} : root(new node()), nodes() {}
void insert(std::string s) { void insert(std::string s) {
std::shared_ptr<node> cur = root; std::shared_ptr<node> cur = root;
for (char c : s) { for (char c : s) {
if (cur->child[c - 'a'] == nullptr) { auto child_ptr = cur->child[c - 'a'].lock();
cur->child[c - 'a'] = std::make_shared<node>();
if (child_ptr == nullptr) {
child_ptr = std::make_shared<node>();
nodes.emplace_back(child_ptr); // Trick: store all nodes in a vector to avoid early expiration of weak_ptr
cur->child[c - 'a'] = child_ptr;
} }
cur = cur->child[c - 'a']; cur = child_ptr;
} }
cur->cnt++; cur->cnt++;
@ -43,9 +46,11 @@ class AcAutomaton {
std::queue<std::shared_ptr<node>> q; std::queue<std::shared_ptr<node>> q;
for (int i = 0; i < 26; i++) { for (int i = 0; i < 26; i++) {
if (root->child[i] != nullptr) { auto child_ptr = root->child[i].lock();
q.emplace(root->child[i]);
root->child[i]->fail = root; if (child_ptr != nullptr) {
q.emplace(child_ptr);
child_ptr->fail = root;
} }
} }
@ -54,12 +59,27 @@ class AcAutomaton {
q.pop(); q.pop();
for (int i = 0; i < 26; i++) { for (int i = 0; i < 26; i++) {
if (cur->child[i] != nullptr) { auto fail_ptr = cur->fail.lock(),
cur->child[i]->fail = cur->fail->child[i] == nullptr ? root : cur->fail->child[i]; child_ptr = cur->child[i].lock();
q.emplace(cur->child[i]); if (child_ptr != nullptr) {
if (fail_ptr != nullptr) {
auto fail_child_ptr = fail_ptr->child[i].lock();
child_ptr->fail = fail_child_ptr == nullptr ? root : fail_child_ptr;
} else {
child_ptr->fail = root;
}
q.emplace(child_ptr);
} else { } else {
cur->child[i] = cur->fail->child[i] == nullptr ? root : cur->fail->child[i]; if (fail_ptr != nullptr) {
auto fail_child_ptr = fail_ptr->child[i].lock();
cur->child[i] = fail_child_ptr == nullptr ? root : fail_child_ptr;
} else {
cur->child[i] = root;
}
} }
} }
} }
@ -67,12 +87,16 @@ class AcAutomaton {
int query(std::string t) { int query(std::string t) {
int res = 0; int res = 0;
std::shared_ptr<node> cur = root; auto cur = root;
for (char c : t) { for (char c : t) {
cur = cur->child[c - 'a'] == nullptr ? root : cur->child[c - 'a']; auto child_ptr = cur->child[c - 'a'].lock();
for (std::shared_ptr<node> i = cur; i != nullptr && i->cnt != -1; i = i->fail) { cur = child_ptr == nullptr ? root : child_ptr;
for (auto i = cur;
i != nullptr && i->cnt != -1;
i = i->fail.lock()) {
res += i->cnt; res += i->cnt;
i->cnt = -1; i->cnt = -1;
} }