Problem p02851 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll, int> plli;
typedef pair<int, pii> pipii;
typedef vector<vector<int>> mati;
typedef vector<vector<double>> matd;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;

#define FOR(i, x, y) for (ll i = (ll)x; i < (ll)y; ++i)
#define REP(i, y) FOR(i, 0, y)
#define RFOR(i, x, y) for (ll i = (ll)x; i >= (ll)y; --i)
#define RREP(i, x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back
#define debug_printf(x...)                                                     \
  cerr << "line " << __LINE__ << " : ";                                        \
  debug_printf_in(x);

template <typename First> void debug_printf_in(First first) {
  cerr << first << endl;
  return;
}

template <typename First, typename... Rest>
void debug_printf_in(First first, Rest... rest) {
  cerr << first << " ";
  debug_printf_in(rest...);
  return;
}

void IN(void) { return; }

template <typename First, typename... Rest>
void IN(First &first, Rest &...rest) {
  cin >> first;
  IN(rest...);
  return;
}

template <typename First> void OUT(First first) {
  cout << first << endl;
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest) {
  cout << first << " ";
  OUT(rest...);
  return;
}

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 (a > b)
    a = b;
};
int popcount(int t) { return __builtin_popcount(t); }  // GCC
int popcount(ll t) { return __builtin_popcountll(t); } // GCC

template <typename T> void vec_print(vector<T> VEC) {
  REP(i, VEC.size()) { cout << VEC[i] << " "; }
  cout << "\n";
};

template <typename T>
void mat_print(vector<vector<T>> MAT){
    REP(i, MAT.size()){REP(j, MAT[i].size()){cout << MAT[i][j] << " ";
}
cout << "\n";
}
}
;

template <typename CLASS1, typename CLASS2> class HOGE {
public:
  CLASS1 key;
  CLASS2 value;
  HOGE(void) { return; };
  HOGE(CLASS1 key, CLASS2 value) {
    this->key = key;
    this->value = value;
  };
  ~HOGE(void) { return; };

  void print(void) {
    cout << "key : " << key << ", value : " << value << "\n";
    return;
  };

  bool operator==(const HOGE &obj) { return (this->value == obj.value); };
  bool operator<(const HOGE &obj) { return (this->value < obj.value); };
  bool operator>(const HOGE &obj) { return (this->value > obj.value); };
};

template <typename CLASS1, typename CLASS2>
bool operator==(const HOGE<CLASS1, CLASS2> &hoge1,
                const HOGE<CLASS1, CLASS2> &hoge2) {
  return hoge1.value == hoge2.value;
};

template <typename CLASS1, typename CLASS2>
bool operator<(const HOGE<CLASS1, CLASS2> &hoge1,
               const HOGE<CLASS1, CLASS2> &hoge2) {
  return hoge1.value < hoge2.value;
};

template <typename CLASS1, typename CLASS2>
bool operator>(const HOGE<CLASS1, CLASS2> &hoge1,
               const HOGE<CLASS1, CLASS2> &hoge2) {
  return hoge1.value > hoge2.value;
};

constexpr int INF = (1 << 30);
constexpr ll INFLL = 1LL << 62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9) + 7);

ll N, K;
vll A;

int main() {
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after
              // std::cin)
  ios::sync_with_stdio(
      false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  IN(N, K);
  A.resize(N);
  REP(i, N) IN(A[i]);
  REP(i, N) A[i]--;
  REP(i, N) A[i] %= K;

  vll L(N + 1, 0);
  L[0] = 0;
  REP(i, N) L[i + 1] = (L[i] + A[i]) % K;

  vll M(K, 0);
  ll ans = 0;
  //(L[i] - L[j]) = 0
  REP(i, N + 1) {
    /*
    debug_printf(i, L[i]);
    REP(j,K){
      debug_printf(M[j]);
    }
    */
    if (i >= K)
      M[L[i - K]]--;
    ans += M[L[i]];
    M[L[i]]++;
    // debug_printf(i, ans);
  }

  OUT(ans);

  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll, int> plli;
typedef pair<int, pii> pipii;
typedef vector<vector<int>> mati;
typedef vector<vector<double>> matd;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;

#define FOR(i, x, y) for (ll i = (ll)x; i < (ll)y; ++i)
#define REP(i, y) FOR(i, 0, y)
#define RFOR(i, x, y) for (ll i = (ll)x; i >= (ll)y; --i)
#define RREP(i, x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back
#define debug_printf(x...)                                                     \
  cerr << "line " << __LINE__ << " : ";                                        \
  debug_printf_in(x);

template <typename First> void debug_printf_in(First first) {
  cerr << first << endl;
  return;
}

template <typename First, typename... Rest>
void debug_printf_in(First first, Rest... rest) {
  cerr << first << " ";
  debug_printf_in(rest...);
  return;
}

void IN(void) { return; }

template <typename First, typename... Rest>
void IN(First &first, Rest &...rest) {
  cin >> first;
  IN(rest...);
  return;
}

template <typename First> void OUT(First first) {
  cout << first << endl;
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest) {
  cout << first << " ";
  OUT(rest...);
  return;
}

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 (a > b)
    a = b;
};
int popcount(int t) { return __builtin_popcount(t); }  // GCC
int popcount(ll t) { return __builtin_popcountll(t); } // GCC

template <typename T> void vec_print(vector<T> VEC) {
  REP(i, VEC.size()) { cout << VEC[i] << " "; }
  cout << "\n";
};

template <typename T>
void mat_print(vector<vector<T>> MAT){
    REP(i, MAT.size()){REP(j, MAT[i].size()){cout << MAT[i][j] << " ";
}
cout << "\n";
}
}
;

template <typename CLASS1, typename CLASS2> class HOGE {
public:
  CLASS1 key;
  CLASS2 value;
  HOGE(void) { return; };
  HOGE(CLASS1 key, CLASS2 value) {
    this->key = key;
    this->value = value;
  };
  ~HOGE(void) { return; };

  void print(void) {
    cout << "key : " << key << ", value : " << value << "\n";
    return;
  };

  bool operator==(const HOGE &obj) { return (this->value == obj.value); };
  bool operator<(const HOGE &obj) { return (this->value < obj.value); };
  bool operator>(const HOGE &obj) { return (this->value > obj.value); };
};

template <typename CLASS1, typename CLASS2>
bool operator==(const HOGE<CLASS1, CLASS2> &hoge1,
                const HOGE<CLASS1, CLASS2> &hoge2) {
  return hoge1.value == hoge2.value;
};

template <typename CLASS1, typename CLASS2>
bool operator<(const HOGE<CLASS1, CLASS2> &hoge1,
               const HOGE<CLASS1, CLASS2> &hoge2) {
  return hoge1.value < hoge2.value;
};

template <typename CLASS1, typename CLASS2>
bool operator>(const HOGE<CLASS1, CLASS2> &hoge1,
               const HOGE<CLASS1, CLASS2> &hoge2) {
  return hoge1.value > hoge2.value;
};

constexpr int INF = (1 << 30);
constexpr ll INFLL = 1LL << 62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9) + 7);

ll N, K;
vll A;

int main() {
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after
              // std::cin)
  ios::sync_with_stdio(
      false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  IN(N, K);
  A.resize(N);
  REP(i, N) IN(A[i]);
  REP(i, N) A[i]--;
  REP(i, N) A[i] %= K;

  vll L(N + 1, 0);
  L[0] = 0;
  REP(i, N) L[i + 1] = (L[i] + A[i]) % K;

  // vll M(K, 0);
  map<ll, ll> M;
  ll ans = 0;
  //(L[i] - L[j]) = 0
  REP(i, N + 1) {
    /*
    debug_printf(i, L[i]);
    REP(j,K){
      debug_printf(M[j]);
    }
    */
    if (i >= K)
      M[L[i - K]]--;
    ans += M[L[i]];
    M[L[i]]++;
    // debug_printf(i, ans);
  }

  OUT(ans);

  return 0;
}