Problem p02665 (C++) — buggy submission, verdict: Runtime Error

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

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define F0R(i, a) FOR(i, 0, a)
#define ROF(i, a, b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i, a) ROF(i, 0, a)

using ll = long long;
using ld = long double;
ll INF = LLONG_MAX;

using vi = vector<int>;
using vll = vector<ll>;
using pii = pair<int, int>;

namespace output {
void pr(int x) { cout << x; }
void pr(long x) { cout << x; }
void pr(ll x) { cout << x; }
void pr(unsigned x) { cout << x; }
void pr(unsigned long x) { cout << x; }
void pr(unsigned long long x) { cout << x; }
void pr(float x) { cout << x; }
void pr(double x) { cout << x; }
void pr(ld x) { cout << x; }
void pr(char x) { cout << x; }
void pr(const char *x) { cout << x; }
void pr(const string &x) { cout << x; }
void pr(bool x) { pr(x ? "true" : "false"); }
template <class T> void pr(const complex<T> &x) { cout << x; }

template <class T1, class T2> void pr(const pair<T1, T2> &x);
template <class T> void pr(const T &x);

template <class T, class... Ts> void pr(const T &t, const Ts &...ts) {
  pr(t);
  pr(ts...);
}
template <class T1, class T2> void pr(const pair<T1, T2> &x) {
  pr("{", x.f, ", ", x.s, "}");
}
template <class T> void pr(const T &x) {
  pr("{"); // const iterator needed for vector<bool>
  bool fst = 1;
  for (const auto &a : x)
    pr(!fst ? ", " : "", a), fst = 0;
  pr("}");
}

void print() { pr("\\n"); } // print w/ spaces
template <class T, class... Ts> void print(const T &t, const Ts &...ts) {
  pr(t);
  if (sizeof...(ts))
    pr(" ");
  print(ts...);
}
} // namespace output

using namespace output;

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  ll N;
  cin >> N;
  vll arr(N + 1);
  F0R(i, N + 1) cin >> arr[i];

  if (N == 0 && arr[0] == 1) {
    print(1);
    return 0;
  }
  vll free(N + 1);
  free[0] = 2;

  vll nodes(N + 1);
  nodes[0] = 1;
  FOR(i, 1, N + 1) {
    if (nodes[i - 1] > (1LL << 50)) {
      nodes[i] = nodes[i - 1];
    } else {
      nodes[i] = 2 * (nodes[i - 1] - arr[i - 1]);
      if (nodes[i] < arr[i]) {
        print(-1);
        return 0;
      }
    }
  }

  ll cur = 0;
  ll ans = 0;
  F0R(i, N + 1) {
    ll X = arr[i];
    while (X > 0 && X >= free[cur]) {
      if (cur >= i) {
        print(-1);
        return 0;
      }
      ll remove = free[cur];
      free[cur] = 0;
      X -= remove;
      ans += remove * (i - cur);
      ++cur;
      free[cur] = nodes[cur] - arr[cur];
    }
    if (X > 0) {
      if (cur >= i) {
        print(-1);
        return 0;
      }
      ans += X * (i - cur);
      free[cur] -= X;
    }
  }
  print(ans + 1);
}


Error: 0

Fixed submission:

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

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define F0R(i, a) FOR(i, 0, a)
#define ROF(i, a, b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i, a) ROF(i, 0, a)

using ll = long long;
using ld = long double;
ll INF = LLONG_MAX;

using vi = vector<int>;
using vll = vector<ll>;
using pii = pair<int, int>;

namespace output {
void pr(int x) { cout << x; }
void pr(long x) { cout << x; }
void pr(ll x) { cout << x; }
void pr(unsigned x) { cout << x; }
void pr(unsigned long x) { cout << x; }
void pr(unsigned long long x) { cout << x; }
void pr(float x) { cout << x; }
void pr(double x) { cout << x; }
void pr(ld x) { cout << x; }
void pr(char x) { cout << x; }
void pr(const char *x) { cout << x; }
void pr(const string &x) { cout << x; }
void pr(bool x) { pr(x ? "true" : "false"); }
template <class T> void pr(const complex<T> &x) { cout << x; }

template <class T1, class T2> void pr(const pair<T1, T2> &x);
template <class T> void pr(const T &x);

template <class T, class... Ts> void pr(const T &t, const Ts &...ts) {
  pr(t);
  pr(ts...);
}
template <class T1, class T2> void pr(const pair<T1, T2> &x) {
  pr("{", x.f, ", ", x.s, "}");
}
template <class T> void pr(const T &x) {
  pr("{"); // const iterator needed for vector<bool>
  bool fst = 1;
  for (const auto &a : x)
    pr(!fst ? ", " : "", a), fst = 0;
  pr("}");
}

void print() { pr("\\n"); } // print w/ spaces
template <class T, class... Ts> void print(const T &t, const Ts &...ts) {
  pr(t);
  if (sizeof...(ts))
    pr(" ");
  print(ts...);
}
} // namespace output

using namespace output;

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  ll N;
  cin >> N;
  vll arr(N + 1);
  F0R(i, N + 1) cin >> arr[i];

  if (arr[0] == 1 && N != 0) {
    print(-1);
    return 0;
  }

  vll free(N + 1);
  free[0] = 2;

  vll nodes(N + 1);
  nodes[0] = 1;
  FOR(i, 1, N + 1) {
    nodes[i] = 2 * (nodes[i - 1] - arr[i - 1]);
    if (nodes[i] < 0) {
      print(-1);
      return 0;
    }
    if (nodes[i] > 1e8)
      break;
  }

  ll cur = 0;
  ll ans = 0;
  F0R(i, N + 1) {
    ll X = arr[i];
    while (X > 0 && X >= free[cur]) {
      if (cur > i) {
        print(-1);
        return 0;
      }
      ll remove = free[cur];
      free[cur] = 0;
      X -= remove;
      ans += remove * (i - cur);
      ++cur;
      free[cur] = nodes[cur] - arr[cur];
    }
    if (X > 0) {
      if (cur > i) {
        print(-1);
        return 0;
      }
      ans += X * (i - cur);
      free[cur] -= X;
    }
  }
  print(ans + 1);
}