Submission #491379

#	Time	Username	Problem	Language	Result	Execution time	Memory
491379		regex0754	Kangaroo (CEOI16_kangaroo)	C++17	0 / 100	2 ms	588 KiB

kangaroo

#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
using namespace std;

using namespace __gnu_pbds;
template <typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
// find_by_order(k) -> iterator of kth element (in sorted fashion : low - high)
// order_of_key(x) -> #numbers strictly less than x

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

#define sync ios_base::sync_with_stdio(0); cin.tie(0);
#define all(x) x.begin(),x.end()
#define unq(a) sort(all(a));a.resize(unique(all(a)) - a.begin())
#define fi first
#define se second
#define endl '\n'
 
using ll = long long
;using ld = long double;
using pii = pair<int , int>;
 
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//mt19937 rng(0);

const int mod = 1e9 + 7;
template <typename T>
class Modular {
 public:
  using Type = typename decay<decltype(T::value)>::type;

  constexpr Modular() : value() {}
  template <typename U>
  Modular(const U& x) {
    value = normalize(x);
  }

  template <typename U>
  static Type normalize(const U& x) {
    Type v;
    if (-mod() <= x && x < mod()) v = static_cast<Type>(x);
    else v = static_cast<Type>(x % mod());
    if (v < 0) v += mod();
    return v;
  }

  const Type& operator()() const { return value; }
  template <typename U>
  explicit operator U() const { return static_cast<U>(value); }
  constexpr static Type mod() { return T::value; }

  Modular& operator+=(const Modular& other) { if ((value += other.value) >= mod()) value -= mod(); return *this; }
  Modular& operator-=(const Modular& other) { if ((value -= other.value) < 0) value += mod(); return *this; }
  template <typename U> Modular& operator+=(const U& other) { return *this += Modular(other); }
  template <typename U> Modular& operator-=(const U& other) { return *this -= Modular(other); }
  Modular& operator++() { return *this += 1; }
  Modular& operator--() { return *this -= 1; }
  Modular operator++(int) { Modular result(*this); *this += 1; return result; }
  Modular operator--(int) { Modular result(*this); *this -= 1; return result; }
  Modular operator-() const { return Modular(-value); }

  template <typename U = T>
  typename enable_if<is_same<typename Modular<U>::Type, int>::value, Modular>::type& operator*=(const Modular& rhs) {
    value = normalize(static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value));
    return *this;
  }
  template <typename U = T>
  typename enable_if<is_same<typename Modular<U>::Type, int64_t>::value, Modular>::type& operator*=(const Modular& rhs) {
    int64_t q = static_cast<int64_t>(static_cast<long double>(value) * rhs.value / mod());
    value = normalize(value * rhs.value - q * mod());
    return *this;
  }
  template <typename U = T>
  typename enable_if<!is_integral<typename Modular<U>::Type>::value, Modular>::type& operator*=(const Modular& rhs) {
    value = normalize(value * rhs.value);
    return *this;
  }

  Modular inverse() const {
    Type a = value, b = mod(), u = 0, v = 1;
    while (a != 0) {
      Type t = b / a;
      b -= t * a; swap(a, b);
      u -= t * v; swap(u, v);
    }
    assert(b == 1);
    return Modular(u);
  }
  Modular& operator/=(const Modular& other) { return *this *= other.inverse(); }

  template <typename U>
  friend bool operator==(const Modular<U>& lhs, const Modular<U>& rhs);

  template <typename U>
  friend std::istream& operator>>(std::istream& stream, Modular<U>& number);

 private:
  Type value;
};

template <typename T> bool operator==(const Modular<T>& lhs, const Modular<T>& rhs) { return lhs.value == rhs.value; }
template <typename T, typename U> bool operator==(const Modular<T>& lhs, U rhs) { return lhs == Modular<T>(rhs); }
template <typename T, typename U> bool operator==(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) == rhs; }

template <typename T> bool operator!=(const Modular<T>& lhs, const Modular<T>& rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(const Modular<T>& lhs, U rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(U lhs, const Modular<T>& rhs) { return !(lhs == rhs); }

template <typename T> Modular<T> operator+(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) += rhs; }
template <typename T, typename U> Modular<T> operator+(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) += rhs; }
template <typename T, typename U> Modular<T> operator+(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) += rhs; }

template <typename T> Modular<T> operator-(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) -= rhs; }
template <typename T, typename U> Modular<T> operator-(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) -= rhs; }
template <typename T, typename U> Modular<T> operator-(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) -= rhs; }

template <typename T> Modular<T> operator*(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) *= rhs; }
template <typename T, typename U> Modular<T> operator*(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) *= rhs; }
template <typename T, typename U> Modular<T> operator*(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) *= rhs; }

template <typename T> Modular<T> operator/(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) /= rhs; }
template <typename T, typename U> Modular<T> operator/(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) /= rhs; }
template <typename T, typename U> Modular<T> operator/(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) /= rhs; }

template<typename T, typename U>
Modular<T> power(const Modular<T>& a, const U& b) {
  assert(b >= 0);
  Modular<T> x = a, res = 1;
  U p = b;
  while (p > 0) {
    if (p & 1) res *= x;
    x *= x;
    p >>= 1;
  }
  return res;
}

template <typename T>
string to_string(const Modular<T>& number) {
  return to_string(number());
}

template <typename T>
std::ostream& operator<<(std::ostream& stream, const Modular<T>& number) {
  return stream << number();
}

template <typename T>
std::istream& operator>>(std::istream& stream, Modular<T>& number) {
  stream >> number.value;
  number.value = Modular<T>::normalize(number.value);
  return stream;
}

struct VarMod { static int value; };
int VarMod::value;

using mint = Modular<std::integral_constant<int, mod>>;

int main(){
  sync
  //#ifndef ONLINE_JUDGE 
    freopen("kangaroo.in", "r", stdin);
    freopen("kangaroo.out", "w", stdout);
  //#endif


  int tt = 1;
  //cin >> tt;

  while(tt--){
    int n, s, e;
    cin >> n >> s >> e;
    vector<vector<vector<mint>>> dp(n + 1, vector<vector<mint>>(n + 1, vector<mint>(4)));
    for (int i = 0; i <= n; i++){
      if (i){
        if (i == s or i == e){
          dp[i] = dp[i - 1];
          continue;
        }
        for (int pc = 2; pc <= n - 1; pc++){
          for (int msk = 0; msk < 4; msk++){
            //merge edge
            if (pc != 2){
              int l = ((msk >> 1) ? 1 : (i > s));
              if (l)
                dp[i][pc - 1][msk | 2] += dp[i - 1][pc][msk];
              int r = ((msk & 1) ? 1 : (i > e));
              if (r)
                dp[i][pc - 1][msk | 1] += dp[i - 1][pc][msk];
            } 
            else{
              int l = ((msk >> 1) ? 1 : (i > s));
              int r = ((msk & 1) ? 1 : (i > e));
              if (l && r){
                dp[i][pc - 1][3] += dp[i - 1][pc][msk];
              }
            }
            // merge inside component
            dp[i][pc - 1][msk] += (max(0, (pc - 3)) * dp[i - 1][pc][msk]);
            // append only possible for edge components
            if (i < s && 1 - (msk >> 1)){
              dp[i][pc][msk | 2] += dp[i - 1][pc][msk];
            }
            if (i < e && 1 - (msk & 1)){
              dp[i][pc][msk | 1] += dp[i - 1][pc][msk];
            }
            // new component
            dp[i][pc + 1][msk] += ((pc - 1) * dp[i - 1][pc][msk]);
          }
        }
      }
      else{
        if (n == 2) dp[0][1][3] = 1;
        else dp[0][2][0] = 1;
      }
    }
    // for (int i = 1; i <= n; i++){
    //   for (int j = 1; j <= n; j++){
    //     for (int msk = 0; msk < 4; msk++){
    //       cout << i << " " << j << " " << bitset<2>(msk) << " " << dp[i][j][msk] << endl;
    //     } 
    //   }
    // }
    cout << dp[n][1][3] << endl;
  }

  cerr << "processor time: " << clock() / (double) CLOCKS_PER_SEC << "s    ";
  return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:165:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  165 |     freopen("kangaroo.in", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:166:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  166 |     freopen("kangaroo.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49