Submission #387571

#	Time	Username	Problem	Language	Result	Execution time	Memory
387571		rama_pang	Road Construction (JOI21_road_construction)	C++17	100 / 100	7742 ms	19464 KiB

road_construction

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

using lint = long long;
const lint inf = 1e18;

class Fenwick {
 public:
  int sz;
  vector<int> tree;

  Fenwick(int sz) : sz(sz), tree(sz, 0) {}

  void Update(int p, int x) {
    for (int i = p; i < sz; i |= i + 1) {
      tree[i] += x;
    }
  }

  int Query(int p) {
    int res = 0;
    for (int i = p; i > 0; i &= i - 1) {
      res += tree[i - 1];
    }
    return res;
  }
};

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);

  int N, K;
  cin >> N >> K;

  vector<lint> X(N), Y(N);
  vector<lint> coordX = {-inf, inf}, coordY = {-inf, inf};

  for (int i = 0; i < N; i++) {
    cin >> X[i] >> Y[i];
    tie(X[i], Y[i]) = make_pair(X[i] + Y[i], X[i] - Y[i]);
    coordX.emplace_back(X[i]);
    coordY.emplace_back(Y[i]);
  }

  sort(begin(coordX), end(coordX));
  sort(begin(coordY), end(coordY));
  coordX.resize(unique(begin(coordX), end(coordX)) - begin(coordX));
  coordY.resize(unique(begin(coordY), end(coordY)) - begin(coordY));

  vector<int> ord(N);
  iota(begin(ord), end(ord), 0);
  sort(begin(ord), end(ord), [&](int i, int j) { return X[i] < X[j]; });

  const auto Count = [&](lint dist) {
    Fenwick F(coordY.size());
    const auto Modify = [&](int i, int x) {
      int yid = lower_bound(begin(coordY), end(coordY), Y[i]) - begin(coordY);
      F.Update(yid, x);
    };

    lint res = 0;
    for (int i = 0, j = 0; i < N; i++) {
      while (abs(X[ord[i]] - X[ord[j]]) > dist) Modify(ord[j++], -1);
      int ylo = lower_bound(begin(coordY), end(coordY), Y[ord[i]] - dist) - begin(coordY);
      int yhi = upper_bound(begin(coordY), end(coordY), Y[ord[i]] + dist) - begin(coordY);
      res += F.Query(yhi) - F.Query(ylo);
      Modify(ord[i], 1);
    }

    return res;
  };

  const auto Generate = [&](lint dist) -> vector<lint> {
    set<pair<lint, int>> F;
    const auto Modify = [&](int i, int x) {
      if (x == 1) {
        F.emplace(Y[i], i);
      } else if (x == -1) {
        F.erase({Y[i], i});
      }
    };

    vector<pair<int, int>> pairs;
    for (int i = 0, j = 0; i < N; i++) {
      while (abs(X[ord[i]] - X[ord[j]]) > dist) Modify(ord[j++], -1);
      int ylo = lower_bound(begin(coordY), end(coordY), Y[ord[i]] - dist) - begin(coordY);
      int yhi = upper_bound(begin(coordY), end(coordY), Y[ord[i]] + dist) - begin(coordY);
      auto it = F.lower_bound({Y[ord[i]] - dist, -1});
      while (it != end(F) && abs(it->first - Y[ord[i]]) <= dist) {
        pairs.emplace_back(ord[i], it->second);
        it++;
      }
      Modify(ord[i], 1);
    }

    vector<lint> res;
    for (auto [i, j] : pairs) {
      if (i != j) {
        res.emplace_back(max(abs(X[i] - X[j]), abs(Y[i] - Y[j])));
      }
    }

    return res;
  };

  lint lo = 0, hi = 1e10;
  while (lo < hi) {
    lint md = (lo + hi) / 2;
    if (Count(md) >= K) {
      hi = md;
    } else {
      lo = md + 1;
    }
  }

  vector<lint> ans = Generate(lo - 1);
  while (ans.size() < K) {
    ans.emplace_back(lo);
  }

  sort(begin(ans), end(ans));
  assert(ans.size() == K);
  for (int i = 0; i < K; i++) {
    cout << ans[i] << '\n';
  }
  return 0;
}

Compilation message (stderr)

road_construction.cpp: In lambda function:
road_construction.cpp:87:11: warning: unused variable 'ylo' [-Wunused-variable]
   87 |       int ylo = lower_bound(begin(coordY), end(coordY), Y[ord[i]] - dist) - begin(coordY);
      |           ^~~
road_construction.cpp:88:11: warning: unused variable 'yhi' [-Wunused-variable]
   88 |       int yhi = upper_bound(begin(coordY), end(coordY), Y[ord[i]] + dist) - begin(coordY);
      |           ^~~
road_construction.cpp: In function 'int main()':
road_construction.cpp:118:21: warning: comparison of integer expressions of different signedness: 'std::vector<long long int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  118 |   while (ans.size() < K) {
      |          ~~~~~~~~~~~^~~
In file included from /usr/include/c++/9/cassert:44,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:33,
                 from road_construction.cpp:1:
road_construction.cpp:123:21: warning: comparison of integer expressions of different signedness: 'std::vector<long long int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  123 |   assert(ans.size() == K);
      |          ~~~~~~~~~~~^~~~

• Subtask 1: 5 / 5
• Subtask 2: 6 / 6
• Subtask 3: 7 / 7
• Subtask 4: 20 / 20
• Subtask 5: 27 / 27
• Subtask 6: 35 / 35