Problem p03946 (C++)

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

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
typedef vector<ll> Vec;
typedef vector<int> Vi;
typedef vector<string> Vs;
typedef vector<P> VP;
typedef vector<vector<ll>> VV;
typedef vector<vector<int>> VVi;

#define REP(i, a, b) for (ll i = (a); i < (b); i++)
#define PER(i, a, b) for (ll i = (a); i >= (b); i--)
#define rep(i, n) REP(i, 0, n)
#define per(i, n) PER(i, n, 0)
const ll INF = 1e18 + 18;
const ll MAX = 100005;
const ll MOD = 1000000007;
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl;
#define YES(n) cout << ((n) ? "YES" : "NO") << endl;
#define ALL(v) v.begin(), v.end()
#define rALL(v) v.rbegin(), v.rend()
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a, b)
#define Each(a, b) for (auto &a : b)
#define REPM(i, mp) for (auto i = mp.begin(); i != mp.end(); ++i)
#define dbg(x_) cerr << #x_ << ":" << x_ << endl;
#define dbgmap(mp)                                                             \
  cerr << #mp << ":" << endl;                                                  \
  for (auto i = mp.begin(); i != mp.end(); ++i) {                              \
    cerr << i->first << ":" << i->second << endl;                              \
  }
#define dbgarr(n, m, arr)                                                      \
  rep(i, n) {                                                                  \
    rep(j, m) { cerr << arr[i][j] << " "; }                                    \
    cerr << endl;                                                              \
  }
#define dbgdp(n, arr)                                                          \
  rep(i, n) { cerr << arr[i] << " "; }                                         \
  cerr << endl;
#define dbgmint(n, arr)                                                        \
  rep(i, n) { cerr << arr[i].x << " "; }                                       \
  cerr << endl;
#define out(a) cout << a << endl
#define out2(a, b) cout << a << " " << b << endl
#define vout(v)                                                                \
  rep(i, v.size()) { cout << v[i] << " "; }                                    \
  cout << endl
#define Uniq(v) v.erase(unique(v.begin(), v.end()), v.end())
#define fi first
#define se second

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &p) {
  return s << "(" << p.first << ", " << p.second << ")";
}

template <typename T> istream &operator>>(istream &i, vector<T> &v) {
  rep(j, v.size()) i >> v[j];
  return i;
}

// vector
template <typename T> ostream &operator<<(ostream &s, const vector<T> &v) {
  int len = v.size();
  for (int i = 0; i < len; ++i) {
    s << v[i];
    if (i < len - 1)
      s << "	";
  }
  return s;
}

// 2 dimentional vector
template <typename T>
ostream &operator<<(ostream &s, const vector<vector<T>> &vv) {
  int len = vv.size();
  for (int i = 0; i < len; ++i) {
    s << vv[i] << endl;
  }
  return s;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << std::setprecision(10);

  ll n, t;
  cin >> n >> t;
  Vec a(n);
  cin >> a;
  Vec m(n + 1);
  m[n + 1] = 0;
  per(i, n - 1) { chmax(m[i], max(m[i + 1], a[i])); }
  map<ll, ll> mp;
  rep(i, n) { mp[a[i]]++; }
  ll k = 0;
  rep(i, n) { chmax(k, m[i] - a[i]); }
  ll ans = 0;

  rep(i, n) {
    if (m[i] - a[i] == k) {
      ans += mp[a[i] + k];
    }
  }
  cout << ans << endl;
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
typedef vector<ll> Vec;
typedef vector<int> Vi;
typedef vector<string> Vs;
typedef vector<P> VP;
typedef vector<vector<ll>> VV;
typedef vector<vector<int>> VVi;

#define REP(i, a, b) for (ll i = (a); i < (b); i++)
#define PER(i, a, b) for (ll i = (a); i >= (b); i--)
#define rep(i, n) REP(i, 0, n)
#define per(i, n) PER(i, n, 0)
const ll INF = 1e18 + 18;
const ll MAX = 100005;
const ll MOD = 1000000007;
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl;
#define YES(n) cout << ((n) ? "YES" : "NO") << endl;
#define ALL(v) v.begin(), v.end()
#define rALL(v) v.rbegin(), v.rend()
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a, b)
#define Each(a, b) for (auto &a : b)
#define REPM(i, mp) for (auto i = mp.begin(); i != mp.end(); ++i)
#define dbg(x_) cerr << #x_ << ":" << x_ << endl;
#define dbgmap(mp)                                                             \
  cerr << #mp << ":" << endl;                                                  \
  for (auto i = mp.begin(); i != mp.end(); ++i) {                              \
    cerr << i->first << ":" << i->second << endl;                              \
  }
#define dbgarr(n, m, arr)                                                      \
  rep(i, n) {                                                                  \
    rep(j, m) { cerr << arr[i][j] << " "; }                                    \
    cerr << endl;                                                              \
  }
#define dbgdp(n, arr)                                                          \
  rep(i, n) { cerr << arr[i] << " "; }                                         \
  cerr << endl;
#define dbgmint(n, arr)                                                        \
  rep(i, n) { cerr << arr[i].x << " "; }                                       \
  cerr << endl;
#define out(a) cout << a << endl
#define out2(a, b) cout << a << " " << b << endl
#define vout(v)                                                                \
  rep(i, v.size()) { cout << v[i] << " "; }                                    \
  cout << endl
#define Uniq(v) v.erase(unique(v.begin(), v.end()), v.end())
#define fi first
#define se second

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &p) {
  return s << "(" << p.first << ", " << p.second << ")";
}

template <typename T> istream &operator>>(istream &i, vector<T> &v) {
  rep(j, v.size()) i >> v[j];
  return i;
}

// vector
template <typename T> ostream &operator<<(ostream &s, const vector<T> &v) {
  int len = v.size();
  for (int i = 0; i < len; ++i) {
    s << v[i];
    if (i < len - 1)
      s << "	";
  }
  return s;
}

// 2 dimentional vector
template <typename T>
ostream &operator<<(ostream &s, const vector<vector<T>> &vv) {
  int len = vv.size();
  for (int i = 0; i < len; ++i) {
    s << vv[i] << endl;
  }
  return s;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << std::setprecision(10);

  ll n, t;
  cin >> n >> t;
  Vec a(n);
  cin >> a;
  Vec m(n + 1);
  m[n] = 0;
  per(i, n - 1) { chmax(m[i], max(m[i + 1], a[i])); }
  map<ll, ll> mp;
  rep(i, n) { mp[a[i]]++; }
  ll k = 0;
  rep(i, n) { chmax(k, m[i] - a[i]); }
  ll ans = 0;

  rep(i, n) {
    if (m[i] - a[i] == k) {
      ans += mp[a[i] + k];
    }
  }
  cout << ans << endl;
  return 0;
}