Problem p02851 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cassert>
#include <cmath>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string.h>
#include <string>
#include <unistd.h>
#include <unordered_map>
#include <vector>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vvvl> vvvvl;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<char> vc;
typedef vector<vector<char>> vvc;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<vvd> vvvd;
typedef pair<ll, ll> PL;
typedef vector<PL> vpl;
typedef vector<vector<PL>> vvpl;
typedef vector<vvpl> vvvpl;
typedef pair<ll, PL> TL;
typedef vector<TL> vtl;
typedef vector<vtl> vvtl;
const int INF = 1001001001;
const ll LINF = 1e18;
const double pi = 3.1415926535897932;
const string endstr = "\n";
#define FOR(i, a, b) for (ll i = (a); i < b; i++)
#define RFOR(i, a, b) for (ll i = (a); i > b; i--)
#define rep(i, n) for (ll i = 0; i < n; i++)
#define rrep(i, n) for (ll i = n - 1; i > -1; i--)
#define FORMAP(it, m) for (auto it = m.begin(); it != m.end(); it++)
#define ff first
#define ss second
#define pb push_back
#define epb emplace_back
#define ALL(X) (X).begin(), (X).end()

template <typename T> T gcd(T a, T b) { return (a == 0) ? b : gcd(b % a, a); }
template <typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

bool p_comp_fs(const PL p1, const PL p2) { return p1.first < p2.first; };
bool p_comp_fg(const PL p1, const PL p2) { return p1.first > p2.first; };
bool p_comp_ss(const PL p1, const PL p2) { return p1.second < p2.second; };
bool p_comp_sg(const PL p1, const PL p2) { return p1.second > p2.second; };
template <typename T> vector<T> uniquen(vector<T> vec) {
  sort(ALL(vec));
  vec.erase(unique(vec.begin(), vec.end()), vec.end());
  return vec;
}

inline ll popcnt(ll x) { return __builtin_popcountll((unsigned long long)x); };
template <class T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
// friend bool operator<(const stc& lhs, const stc& rhs){
//     return std::tie(lhs.l, lhs.r) < std::tie(rhs.l, rhs.r);
// }

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  ll N, K;
  cin >> N >> K;
  vl A(N);
  rep(i, N) {
    cin >> A[i];
    A[i]--;
  }
  vl S(N + 1, 0);
  rep(i, N) S[i + 1] = (A[i] + S[i]) % K;
  ll idx = 0;
  ll ans = 0;
  map<ll, ll> m;
  rep(i, K) m[S[i]]++;
  while (idx < N) {
    //        cerr << m[S[idx]]-1 << endstr;
    ans += m[S[idx]] - 1;
    if (idx + K <= N)
      m[S[idx + K]]++;
    m[S[idx]]--;
    idx++;
  }
  cout << ans << endstr;
  return 0;
}


Fixed submission:
#include <algorithm>
#include <cassert>
#include <cmath>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string.h>
#include <string>
#include <unistd.h>
#include <unordered_map>
#include <vector>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vvvl> vvvvl;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<char> vc;
typedef vector<vector<char>> vvc;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<vvd> vvvd;
typedef pair<ll, ll> PL;
typedef vector<PL> vpl;
typedef vector<vector<PL>> vvpl;
typedef vector<vvpl> vvvpl;
typedef pair<ll, PL> TL;
typedef vector<TL> vtl;
typedef vector<vtl> vvtl;
const int INF = 1001001001;
const ll LINF = 1e18;
const double pi = 3.1415926535897932;
const string endstr = "\n";
#define FOR(i, a, b) for (ll i = (a); i < b; i++)
#define RFOR(i, a, b) for (ll i = (a); i > b; i--)
#define rep(i, n) for (ll i = 0; i < n; i++)
#define rrep(i, n) for (ll i = n - 1; i > -1; i--)
#define FORMAP(it, m) for (auto it = m.begin(); it != m.end(); it++)
#define ff first
#define ss second
#define pb push_back
#define epb emplace_back
#define ALL(X) (X).begin(), (X).end()

template <typename T> T gcd(T a, T b) { return (a == 0) ? b : gcd(b % a, a); }
template <typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

bool p_comp_fs(const PL p1, const PL p2) { return p1.first < p2.first; };
bool p_comp_fg(const PL p1, const PL p2) { return p1.first > p2.first; };
bool p_comp_ss(const PL p1, const PL p2) { return p1.second < p2.second; };
bool p_comp_sg(const PL p1, const PL p2) { return p1.second > p2.second; };
template <typename T> vector<T> uniquen(vector<T> vec) {
  sort(ALL(vec));
  vec.erase(unique(vec.begin(), vec.end()), vec.end());
  return vec;
}

inline ll popcnt(ll x) { return __builtin_popcountll((unsigned long long)x); };
template <class T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
// friend bool operator<(const stc& lhs, const stc& rhs){
//     return std::tie(lhs.l, lhs.r) < std::tie(rhs.l, rhs.r);
// }

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  ll N, K;
  cin >> N >> K;
  vl A(N);
  rep(i, N) {
    cin >> A[i];
    A[i]--;
  }
  vl S(N + 1, 0);
  rep(i, N) S[i + 1] = (A[i] + S[i]) % K;
  ll idx = 0;
  ll ans = 0;
  map<ll, ll> m;
  rep(i, min(K, N + 1)) m[S[i]]++;
  while (idx < N) {
    //        cerr << m[S[idx]]-1 << endstr;
    ans += m[S[idx]] - 1;
    if (idx + K <= N)
      m[S[idx + K]]++;
    m[S[idx]]--;
    idx++;
  }
  cout << ans << endstr;
  return 0;
}