Problem p02649 (C++)

Buggy submission (status: Time Limit Exceeded):
#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;

// not a multiset
// find_by_order(k) -> itr of k-th(0-based) element
// order_of_key(k) -> index of lower_bound(k)
using ordered_set = tree<int, null_type, less<int>, rb_tree_tag,
                         tree_order_statistics_node_update>;

// https://codeforces.com/blog/entry/62393
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }

  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};

template <class t, class u> using hash_table = gp_hash_table<t, u, custom_hash>;

// count が使えない
// find を，しようね！
// move コンストラクタがないのでマージテクで壊れる バカ

using ll = long long;
#define int ll

#define rng(i, a, b) for (int i = int(a); i < int(b); i++)
#define rep(i, b) rng(i, 0, b)
#define gnr(i, a, b) for (int i = int(b) - 1; i >= int(a); i--)
#define per(i, b) gnr(i, 0, b)
#define pb push_back
#define eb emplace_back
#define a first
#define b second
#define bg begin()
#define ed end()
#define all(x) x.bg, x.ed
#define si(x) int(x.size())
#ifdef LOCAL
#define dmp(x) cerr << __LINE__ << " " << #x << " " << x << endl
#else
#define dmp(x) void(0)
#endif

template <class t, class u> void chmax(t &a, u b) {
  if (a < b)
    a = b;
}
template <class t, class u> void chmin(t &a, u b) {
  if (b < a)
    a = b;
}

template <class t> using vc = vector<t>;
template <class t> using vvc = vc<vc<t>>;

using pi = pair<int, int>;
using vi = vc<int>;

template <class t, class u>
ostream &operator<<(ostream &os, const pair<t, u> &p) {
  return os << "{" << p.a << "," << p.b << "}";
}

template <class t> ostream &operator<<(ostream &os, const vc<t> &v) {
  os << "{";
  for (auto e : v)
    os << e << ",";
  return os << "}";
}

#define mp make_pair
#define mt make_tuple
#define one(x) memset(x, -1, sizeof(x))
#define zero(x) memset(x, 0, sizeof(x))
#ifdef LOCAL
void dmpr(ostream &os) { os << endl; }
template <class T, class... Args>
void dmpr(ostream &os, const T &t, const Args &...args) {
  os << t << " ";
  dmpr(os, args...);
}
#define dmp2(...) dmpr(cerr, __LINE__, ##__VA_ARGS__)
#else
#define dmp2(...) void(0)
#endif

using uint = unsigned;
using ull = unsigned long long;

template <class t, size_t n>
ostream &operator<<(ostream &os, const array<t, n> &a) {
  return os << vc<t>(all(a));
}

template <int i, class T> void print_tuple(ostream &, const T &) {}

template <int i, class T, class H, class... Args>
void print_tuple(ostream &os, const T &t) {
  if (i)
    os << ",";
  os << get<i>(t);
  print_tuple<i + 1, T, Args...>(os, t);
}

template <class... Args>
ostream &operator<<(ostream &os, const tuple<Args...> &t) {
  os << "{";
  print_tuple<0, tuple<Args...>, Args...>(os, t);
  return os << "}";
}

template <class t> void print(t x, int suc = 1) {
  cout << x;
  if (suc == 1)
    cout << "\n";
  if (suc == 2)
    cout << " ";
}

ll read() {
  ll i;
  cin >> i;
  return i;
}

vi readvi(int n, int off = 0) {
  vi v(n);
  rep(i, n) v[i] = read() + off;
  return v;
}

template <class T> void print(const vector<T> &v, int suc = 1) {
  rep(i, v.size()) print(v[i], i == int(v.size()) - 1 ? suc : 2);
}

string readString() {
  string s;
  cin >> s;
  return s;
}

template <class T> T sq(const T &t) { return t * t; }

// #define CAPITAL
void yes(bool ex = true) {
#ifdef CAPITAL
  cout << "YES"
       << "\n";
#else
  cout << "Yes"
       << "\n";
#endif
  if (ex)
    exit(0);
}
void no(bool ex = true) {
#ifdef CAPITAL
  cout << "NO"
       << "\n";
#else
  cout << "No"
       << "\n";
#endif
  if (ex)
    exit(0);
}
void possible(bool ex = true) {
#ifdef CAPITAL
  cout << "POSSIBLE"
       << "\n";
#else
  cout << "Possible"
       << "\n";
#endif
  if (ex)
    exit(0);
}
void impossible(bool ex = true) {
#ifdef CAPITAL
  cout << "IMPOSSIBLE"
       << "\n";
#else
  cout << "Impossible"
       << "\n";
#endif
  if (ex)
    exit(0);
}

constexpr ll ten(int n) { return n == 0 ? 1 : ten(n - 1) * 10; }

const ll infLL = LLONG_MAX / 3;

#ifdef int
const int inf = infLL;
#else
const int inf = INT_MAX / 2 - 100;
#endif

int topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }
int topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }
int botbit(signed a) { return a == 0 ? 32 : __builtin_ctz(a); }
int botbit(ll a) { return a == 0 ? 64 : __builtin_ctzll(a); }
int popcount(signed t) { return __builtin_popcount(t); }
int popcount(ll t) { return __builtin_popcountll(t); }
bool ispow2(int i) { return i && (i & -i) == i; }
ll mask(int i) { return (ll(1) << i) - 1; }

bool inc(int a, int b, int c) { return a <= b && b <= c; }

template <class t> void mkuni(vc<t> &v) {
  sort(all(v));
  v.erase(unique(all(v)), v.ed);
}

ll rand_int(ll l, ll r) { //[l, r]
#ifdef LOCAL
  static mt19937_64 gen;
#else
  static mt19937_64 gen(chrono::steady_clock::now().time_since_epoch().count());
#endif
  return uniform_int_distribution<ll>(l, r)(gen);
}

template <class t> void myshuffle(vc<t> &a) {
  rep(i, si(a)) swap(a[i], a[rand_int(0, i)]);
}

template <class t> int lwb(const vc<t> &v, const t &a) {
  return lower_bound(all(v), a) - v.bg;
}

void sub(vi a, int len, int k) {
  // dmp2(a,len,k);
  int n = si(a);
  chmin(k, n);
  /*int ans=0;
  rep(bit,1<<n){
          int x=mask(len),y=0;
          rep(i,n)if(bit&1<<i){
                  x&=a[i];
                  y|=a[i];
          }
          if(popcount(bit)<=k&&x==0&&y==mask(len))
                  ans++;
  }
  print(ans);*/
  const int m = mask(len);
  sort(all(a), [&](int i, int j) { return popcount(i) > popcount(j); });
  using ht = hash_table<int, int>;
  vvc<ht> memo(n, vc<ht>(k));
  auto rec = [&](auto self, int i, int j, int x, int y) -> int {
    if (i == n || j == k)
      return x == 0 && y == m;
    int idx = (x << len) + y;
    auto itr = memo[i][j].find(idx);
    if (itr != memo[i][j].ed)
      return itr->b;
    int res = self(self, i + 1, j, x, y);
    res += self(self, i + 1, j + 1, x & a[i], y | a[i]);
    return memo[i][j][idx] = res;
  };
  print(rec(rec, 0, 0, m, 0));
}

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);

  int n, k, s, t;
  cin >> n >> k >> s >> t;
  if ((s & t) != s) {
    dmp(0);
    print(0);
    return 0;
  }
  int dif = t ^ s;
  vi pos;
  rep(i, 18) if (dif & 1 << i) pos.pb(i);
  // dmp(pos);
  vi a;
  rep(_, n) {
    int x;
    cin >> x;
    if ((x & s) != s)
      continue;
    if ((x & ~t))
      continue;
    int y = 0;
    rep(i, si(pos)) y += ((x >> pos[i]) & 1) << i;
    a.pb(y);
  }
  sub(a, si(pos), k);
}


Fixed submission:
#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;

// not a multiset
// find_by_order(k) -> itr of k-th(0-based) element
// order_of_key(k) -> index of lower_bound(k)
using ordered_set = tree<int, null_type, less<int>, rb_tree_tag,
                         tree_order_statistics_node_update>;

// https://codeforces.com/blog/entry/62393
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }

  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};

template <class t, class u> using hash_table = gp_hash_table<t, u, custom_hash>;

// count が使えない
// find を，しようね！
// move コンストラクタがないのでマージテクで壊れる バカ

using ll = long long;
#define int ll

#define rng(i, a, b) for (int i = int(a); i < int(b); i++)
#define rep(i, b) rng(i, 0, b)
#define gnr(i, a, b) for (int i = int(b) - 1; i >= int(a); i--)
#define per(i, b) gnr(i, 0, b)
#define pb push_back
#define eb emplace_back
#define a first
#define b second
#define bg begin()
#define ed end()
#define all(x) x.bg, x.ed
#define si(x) int(x.size())
#ifdef LOCAL
#define dmp(x) cerr << __LINE__ << " " << #x << " " << x << endl
#else
#define dmp(x) void(0)
#endif

template <class t, class u> void chmax(t &a, u b) {
  if (a < b)
    a = b;
}
template <class t, class u> void chmin(t &a, u b) {
  if (b < a)
    a = b;
}

template <class t> using vc = vector<t>;
template <class t> using vvc = vc<vc<t>>;

using pi = pair<int, int>;
using vi = vc<int>;

template <class t, class u>
ostream &operator<<(ostream &os, const pair<t, u> &p) {
  return os << "{" << p.a << "," << p.b << "}";
}

template <class t> ostream &operator<<(ostream &os, const vc<t> &v) {
  os << "{";
  for (auto e : v)
    os << e << ",";
  return os << "}";
}

#define mp make_pair
#define mt make_tuple
#define one(x) memset(x, -1, sizeof(x))
#define zero(x) memset(x, 0, sizeof(x))
#ifdef LOCAL
void dmpr(ostream &os) { os << endl; }
template <class T, class... Args>
void dmpr(ostream &os, const T &t, const Args &...args) {
  os << t << " ";
  dmpr(os, args...);
}
#define dmp2(...) dmpr(cerr, __LINE__, ##__VA_ARGS__)
#else
#define dmp2(...) void(0)
#endif

using uint = unsigned;
using ull = unsigned long long;

template <class t, size_t n>
ostream &operator<<(ostream &os, const array<t, n> &a) {
  return os << vc<t>(all(a));
}

template <int i, class T> void print_tuple(ostream &, const T &) {}

template <int i, class T, class H, class... Args>
void print_tuple(ostream &os, const T &t) {
  if (i)
    os << ",";
  os << get<i>(t);
  print_tuple<i + 1, T, Args...>(os, t);
}

template <class... Args>
ostream &operator<<(ostream &os, const tuple<Args...> &t) {
  os << "{";
  print_tuple<0, tuple<Args...>, Args...>(os, t);
  return os << "}";
}

template <class t> void print(t x, int suc = 1) {
  cout << x;
  if (suc == 1)
    cout << "\n";
  if (suc == 2)
    cout << " ";
}

ll read() {
  ll i;
  cin >> i;
  return i;
}

vi readvi(int n, int off = 0) {
  vi v(n);
  rep(i, n) v[i] = read() + off;
  return v;
}

template <class T> void print(const vector<T> &v, int suc = 1) {
  rep(i, v.size()) print(v[i], i == int(v.size()) - 1 ? suc : 2);
}

string readString() {
  string s;
  cin >> s;
  return s;
}

template <class T> T sq(const T &t) { return t * t; }

// #define CAPITAL
void yes(bool ex = true) {
#ifdef CAPITAL
  cout << "YES"
       << "\n";
#else
  cout << "Yes"
       << "\n";
#endif
  if (ex)
    exit(0);
}
void no(bool ex = true) {
#ifdef CAPITAL
  cout << "NO"
       << "\n";
#else
  cout << "No"
       << "\n";
#endif
  if (ex)
    exit(0);
}
void possible(bool ex = true) {
#ifdef CAPITAL
  cout << "POSSIBLE"
       << "\n";
#else
  cout << "Possible"
       << "\n";
#endif
  if (ex)
    exit(0);
}
void impossible(bool ex = true) {
#ifdef CAPITAL
  cout << "IMPOSSIBLE"
       << "\n";
#else
  cout << "Impossible"
       << "\n";
#endif
  if (ex)
    exit(0);
}

constexpr ll ten(int n) { return n == 0 ? 1 : ten(n - 1) * 10; }

const ll infLL = LLONG_MAX / 3;

#ifdef int
const int inf = infLL;
#else
const int inf = INT_MAX / 2 - 100;
#endif

int topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }
int topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }
int botbit(signed a) { return a == 0 ? 32 : __builtin_ctz(a); }
int botbit(ll a) { return a == 0 ? 64 : __builtin_ctzll(a); }
int popcount(signed t) { return __builtin_popcount(t); }
int popcount(ll t) { return __builtin_popcountll(t); }
bool ispow2(int i) { return i && (i & -i) == i; }
ll mask(int i) { return (ll(1) << i) - 1; }

bool inc(int a, int b, int c) { return a <= b && b <= c; }

template <class t> void mkuni(vc<t> &v) {
  sort(all(v));
  v.erase(unique(all(v)), v.ed);
}

ll rand_int(ll l, ll r) { //[l, r]
#ifdef LOCAL
  static mt19937_64 gen;
#else
  static mt19937_64 gen(chrono::steady_clock::now().time_since_epoch().count());
#endif
  return uniform_int_distribution<ll>(l, r)(gen);
}

template <class t> void myshuffle(vc<t> &a) {
  rep(i, si(a)) swap(a[i], a[rand_int(0, i)]);
}

template <class t> int lwb(const vc<t> &v, const t &a) {
  return lower_bound(all(v), a) - v.bg;
}

void sub(vi a, int len, int k) {
  // dmp2(a,len,k);
  int n = si(a);
  chmin(k, n);
  vvc<int> w(n, vi(n));
  w[0][0] = 1;
  rng(i, 1, n) {
    rep(j, i) {
      w[i][j] += w[i - 1][j];
      w[i][j + 1] += w[i - 1][j];
    }
  }
  rep(i, n) rep(j, n - 1) w[i][j + 1] += w[i][j];
  int ans = 0;
  rep(i, n) {
    vi buf(1 << len);
    rep(j, i) buf[a[i] ^ a[j]]++;
    rep(lv, len) rep(bit, 1 << len) if (bit & 1 << lv) buf[bit] +=
        buf[bit ^ 1 << lv];
    rep(bit, 1 << len) {
      ans += w[buf[bit]][k - 1] * ((len - popcount(bit)) % 2 == 0 ? 1 : -1);
    }
  }
  print(ans);
}

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);

  int n, k, s, t;
  cin >> n >> k >> s >> t;
  if ((s & t) != s) {
    dmp(0);
    print(0);
    return 0;
  }
  int dif = t ^ s;
  vi pos;
  rep(i, 18) if (dif & 1 << i) pos.pb(i);
  // dmp(pos);
  vi a;
  rep(_, n) {
    int x;
    cin >> x;
    if ((x & s) != s)
      continue;
    if ((x & ~t))
      continue;
    int y = 0;
    rep(i, si(pos)) y += ((x >> pos[i]) & 1) << i;
    a.pb(y);
  }
  sub(a, si(pos), k);
}