Submission #3106934

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
using ll = long long;

// never fail to call build() !!
// constructor()
// add(string)
// match(string) : [left, right], vec<tuple<int left, int right, int key>> in
// right-order
/// --- AhoCorasick Library {{{ ///

struct AhoCorasick {
  struct Trie {
    unordered_map< char, Trie* > child;
    Trie* failure = nullptr;
    vector< int > words;
    Trie* add(char c) {
      if(child.count(c)) {
        return child[c];
      } else {
        return child[c] = new Trie;
      }
    }
    Trie* go(char c) {
      if(child.count(c)) {
        return child[c];
      } else {
        if(failure == nullptr) {
          return this;
        } else {
          return failure->go(c);
        }
      }
    }
  };
  Trie* top = new Trie;
  vector< string > dict;
  void add(string word) {
    Trie* now = top;
    for(size_t i = 0; i < word.size(); i++) {
      now = now->add(word[i]);
    }
    now->words.emplace_back(dict.size());
    dict.emplace_back(word);
  }
  void build() {
    queue< Trie* > q;
    q.emplace(top);
    while(q.size()) {
      Trie* now = q.front();
      q.pop();
      for(pair< char, Trie* > ch : now->child) {
        q.emplace(ch.second);
        Trie* failure = ch.second->failure =
          now == top ? top : now->failure->go(ch.first);
        /// only from failure!!
        vector< int >& words = ch.second->words;
        words.insert(end(words), begin(failure->words), end(failure->words));
      }
    }
  }
  vector< tuple< int, int, int > > match(string s) {
    Trie* now = top;
    vector< tuple< int, int, int > > res;
    for(size_t i = 0; i < s.size(); i++) {
      now = now->go(s[i]);
      for(int word : now->words) {
        res.emplace_back(i - dict[word].size() + 1, i, word);
      }
    }
    return res;
  }
};

/// }}}--- ///


int main() {
  std::ios::sync_with_stdio(false), std::cin.tie(0);
  int n; cin >> n;
  AhoCorasick ecasd;
  for(int i = 0; i < n; i++) {
    string t; cin >> t;
    ecasd.add(t);
  }
  ecasd.build();
  string s; cin >> s;
  int m = s.size();
  auto matches = ecasd.match(s);
  const int mod = 1e9 + 7;
  vector<ll> dp(m + 1);
  dp[0] = 1;
  for(auto p : matches) {
    int le, ri, key; tie(le, ri, key) = p;
    dp[ri+1] = (dp[ri+1] + dp[le]) % mod;
  }
  cout << dp[m] << endl;
  return 0;
}

Submission Info

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