Problem p02702 (C++) — buggy submission, verdict: Runtime Error

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
// #pragma GCC optimize("Ofast")
// #define _GLIBCXX_DEBUG
using namespace std;
typedef long double ld;
typedef long long int ll;
typedef unsigned long long int ull;
// #define int ll
typedef vector<int> vi;
typedef vector<char> vc;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef vector<string> vs;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef vector<pair<int, int>> vpii;
typedef vector<vector<int>> vvi;
typedef vector<vector<char>> vvc;
typedef vector<vector<string>> vvs;
typedef vector<vector<ll>> vvll;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define irep(it, stl) for (auto it = stl.begin(); it != stl.end(); it++)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define fin(ans) cout << (ans) << '\\n'
#define mp(p, q) make_pair(p, q)
#define pb(n) push_back(n)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define floatprec(dig) fixed << setprecision(dig)
#define Sort(a) sort(a.begin(), a.end())
#define Rort(a) sort(a.rbegin(), a.rend())
#define MATHPI acos(-1)
#define itn int;
#define invar(typ, var)                                                        \\
  typ var;                                                                     \\
  cin >> var;
int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
struct io {
  io() {
    ios::sync_with_stdio(false);
    cin.tie(0);
  }
};
const int INF = INT_MAX / 2;
const ll LLINF = 1LL << 60;
constexpr ll MOD = 1000000007;
const double EPS = 1e-9;

signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  string s;
  cin >> s;
  ll N;
  N = s.size();
  vector<ll> cnt(2020);
  ll ans = 0;
  cnt[0] = 1;
  int tot = 0;
  int p = 1;
  for (int i = N - 1; i >= 0; i--) {
    tot = (tot + (s[i] - '0') * p) % 2019;
    ans += cnt[tot];
    p = (p * 10) % 2019;
    cnt[tot]++;
  }

  cout << ans << endl;
}

Error: 0

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
// #pragma GCC optimize("Ofast")
// #define _GLIBCXX_DEBUG
using namespace std;
typedef long double ld;
typedef long long int ll;
typedef unsigned long long int ull;
// #define int ll
typedef vector<int> vi;
typedef vector<char> vc;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef vector<string> vs;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef vector<pair<int, int>> vpii;
typedef vector<vector<int>> vvi;
typedef vector<vector<char>> vvc;
typedef vector<vector<string>> vvs;
typedef vector<vector<ll>> vvll;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define irep(it, stl) for (auto it = stl.begin(); it != stl.end(); it++)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define fin(ans) cout << (ans) << '\\n'
#define mp(p, q) make_pair(p, q)
#define pb(n) push_back(n)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define floatprec(dig) fixed << setprecision(dig)
#define Sort(a) sort(a.begin(), a.end())
#define Rort(a) sort(a.rbegin(), a.rend())
#define MATHPI acos(-1)
#define itn int;
#define invar(typ, var)                                                        \\
  typ var;                                                                     \\
  cin >> var;
int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
struct io {
  io() {
    ios::sync_with_stdio(false);
    cin.tie(0);
  }
};
const int INF = INT_MAX / 2;
const ll LLINF = 1LL << 60;
constexpr ll MOD = 1000000007;
const double EPS = 1e-9;

signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  string s;
  cin >> s;

  ll N;
  N = s.size();

  vector<ll> dp(N - 3);
  dp[N - 4] = stoi(s.substr(N - 4, 4)) % 2019;

  // DPで各桁以降のmod 2019を探す
  int p = 10000 % 2019;
  for (int i = N - 5; i >= 0; i--) {
    dp[i] = (dp[i + 1] + (s[i] - '0') * p) % 2019;

    p = (p * 10) % 2019;
  }

  vll cnt(2019);
  cnt[0] = 1;
  rep(i, N - 3) { cnt[dp[i]]++; }

  ll c = 0;
  rep(i, 2019) {
    c += cnt[i] * (cnt[i] - 1) / 2;
    // if(i == 0) c += cnt[i];
  }
  fin(c);
}