#line 1 "string/test/palindromic_tree.yuki263.test.cpp" #define PROBLEM "https://yukicoder.me/problems/no/263" #line 2 "string/palindromic_tree.hpp" #include #include #include // Palindromic tree / Eertree (回文木) namespace palindromic_tree { template class Node { int suffix_link_; // このノードからのsuffix link (suffix の最長回文) int length_; // このノードが表す回文の長さ。 -1 となる場合もあるので注意 std::map children; public: explicit Node(int suffix_link, int length) : suffix_link_(suffix_link), length_(length) {} int suffix_link() const { return suffix_link_; } int length() const { return length_; } int get_child(Key c) const { auto it = children.find(c); return (it == children.end()) ? -1 : it->second; } void set_child(int c, int nxt_idx) { children[c] = nxt_idx; } template friend OStream &operator<<(OStream &os, const Node &node) { os << "Node(suffix_link=" << node.suffix_link() << ", length=" << node.length() << ", children={"; for (const auto &[c, nxt] : node.children) os << c << "->" << nxt << ", "; return os << "})"; } }; template struct Tree { std::vector> nodes; Tree() { nodes = {Node(-1, -1), Node(0, 0)}; } // nodes[cursor] は s[0:i] の suffix palindrome を表す // 本関数はその nodes[cursor] の suffix palindrome であって更に s[0:(i + 1)] の suffix link となりうる最長のものを返す int find_next_suffix(const std::vector &s, int i, int cursor) { while (true) { if (cursor < 0) return 0; const int cur_len = nodes.at(cursor).length(); const int opposite_pos = i - cur_len - 1; if (opposite_pos >= 0 and s.at(opposite_pos) == s.at(i)) return cursor; cursor = nodes.at(cursor).suffix_link(); } } // 文字列 s を追加する。 Complexity: O(|s|) // callback(i, cursor) は s[0:(i + 1)] が追加された後の nodes[cursor] に対して行う処理 template void add_string(const std::vector &s, Callback callback) { int cursor = 1; for (int i = 0; i < (int)s.size(); ++i) { cursor = find_next_suffix(s, i, cursor); int ch = nodes.at(cursor).get_child(s.at(i)); if (ch < 0) { const int nxt_cursor = nodes.size(); const int new_length = nodes.at(cursor).length() + 2; int new_suffix_link_par = find_next_suffix(s, i, nodes.at(cursor).suffix_link()); int new_suffix_link = nodes.at(new_suffix_link_par).get_child(s.at(i)); if (new_suffix_link < 0) new_suffix_link = 1; nodes.at(cursor).set_child(s.at(i), nxt_cursor); nodes.push_back(Node(new_suffix_link, new_length)); cursor = nxt_cursor; } else { cursor = ch; } callback(i, cursor); } } template void add_string(const std::string &s, Callback callback) { add_string(std::vector{s.cbegin(), s.cend()}, callback); } template void add_string(const Vec &s) { add_string(s, [](int, int) {}); } }; } // namespace palindromic_tree #line 3 "string/test/palindromic_tree.yuki263.test.cpp" #include #include #line 8 "string/test/palindromic_tree.yuki263.test.cpp" using namespace std; int main() { cin.tie(nullptr), ios::sync_with_stdio(false); string S, T; cin >> S >> T; palindromic_tree::Tree tree; vector visitcnt(S.size() + T.size() + 2); tree.add_string(S, [&](int, int node_idx) { visitcnt.at(node_idx)++; }); tree.add_string(T); assert(visitcnt.at(0) == 0); assert(visitcnt.at(1) == 0); const int V = tree.nodes.size(); for (int v = V - 1; v > 0; --v) { visitcnt.at(tree.nodes.at(v).suffix_link()) += visitcnt.at(v); } visitcnt.at(0) = visitcnt.at(1) = 0; for (int v = 1; v < V; ++v) visitcnt.at(v) += visitcnt.at(tree.nodes.at(v).suffix_link()); long long ret = 0; tree.add_string(T, [&](int, int node_idx) { ret += visitcnt.at(node_idx); }); cout << ret << '\n'; }