Submission #22868795

---

Source Code Expand

#include <bits/stdc++.h>
#define sz(c) int(c.size())
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define per(i, a, b) for (int i = (b)-1; i >= (a); --i)
using namespace std;
using ll = long long;

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#ifdef LOCAL
#include <local/debug.h>
#else
#define debug(...) (void)0
#endif

int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  int N;
  cin >> N;
  vector<int> A(N);
  rep(i, 0, N) cin >> A[i];
  vector<int> B(N);
  rep(i, 0, N) cin >> B[i];

  set<pair<int, int>> s;
  ordered_set<int> ord;
  rep(i, 0, N) {
    s.insert({A[i] + i, i + 1});
    ord.insert(i + 1);
  }

  ll res = 0;
  rep(i, 0, N) {
    int val = B[i] + i;
    auto it = s.lower_bound({val, 0});
    if (it == s.end() || it->first != val) {
      if (it != s.end())
        assert(it->first > val);
      res = -1;
      break;
    }

    int pos = it->second;
    ll order = ord.order_of_key(pos);
    res += order;
    debug(val, pos, order);
    s.erase(it);
    ord.erase(pos);
  }

  cout << res << '\n';
}

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