Submission #329271

#	Time	Username	Problem	Language	Result	Execution time	Memory
329271		quocnguyen1012	Meetings (JOI19_meetings)	C++14	100 / 100	1200 ms	1088 KiB

meetings

#ifndef LOCAL
#include "meetings.h"
#endif // LOCAL
#ifdef LOCAL
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <set>
#include <utility>
#include <vector>

namespace {

const int MAX_N = 2000;
const int MAX_CALLS = 100000;

void WrongAnswer(int code) {
  printf("Wrong Answer [%d]\n", code);
  exit(0);
}

int N, num_calls;
std::vector<int> graph[MAX_N];
std::set<std::pair<int, int>> edges, edges_reported;

int weight[MAX_N];

bool Visit(int p, int e, int rt = -1) {
  if (p == e) {
    ++weight[p];
    return true;
  }
  for (int q : graph[p]) {
    if (q != rt) {
      if (Visit(q, e, p)) {
        ++weight[p];
        return true;
      }
    }
  }
  return false;
}

}  // namespace

int Query(int u, int v, int w) {
  if (!(0 <= u && u <= N - 1 && 0 <= v && v <= N - 1 && 0 <= w && w <= N - 1 &&
        u != v && u != w && v != w)) {
    WrongAnswer(1);
  }
  if (++num_calls > MAX_CALLS) {
    WrongAnswer(2);
  }
  std::fill(weight, weight + N, 0);
  Visit(u, v);
  Visit(u, w);
  Visit(v, w);
  for (int x = 0; x < N; ++x) {
    if (weight[x] == 3) {
      return x;
    }
  }
  printf("Error: the input may be invalid\n");
  exit(0);
}

void Bridge(int u, int v) {
  if (!(0 <= u && u < v && v <= N - 1)) {
    WrongAnswer(3);
  }
  if (!(edges.count(std::make_pair(u, v)) >= 1)) {
    WrongAnswer(4);
  }
  if (!(edges_reported.count(std::make_pair(u, v)) == 0)) {
    WrongAnswer(5);
  }
  edges_reported.insert(std::make_pair(u, v));
}

void Solve(int N);

int main() {
#ifdef LOCAL
	freopen("A.INP", "r", stdin);
	freopen("A.OUT", "w", stdout);
#endif // LOCAL
  if (scanf("%d", &N) != 1) {
    fprintf(stderr, "Error while reading input\n");
    exit(1);
  }
  for (int i = 0; i < N - 1; ++i) {
    int u, v;
    if (scanf("%d%d", &u, &v) != 2) {
      fprintf(stderr, "Error while reading input\n");
      exit(1);
    }
    graph[u].push_back(v);
    graph[v].push_back(u);
    edges.insert(std::make_pair(u, v));
  }

  num_calls = 0;
  Solve(N);
  if (edges_reported.size() != static_cast<size_t>(N - 1)) {
    WrongAnswer(6);
  }
  printf("Accepted: %d\n", num_calls);
  return 0;
}
#endif // LOCAL

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int maxn = 2005;

vector<int> sub[maxn];
int n;

int query(int x, int y, int z) {
  if (x == y || z == x) return x;
  if (y == z) return y;
  return Query(x, y, z);
}

void dfs(int root) {
  if (sub[root].empty()) return;
  int v = sub[root][rng() % sub[root].size()];
  vector<int> path;
  vector<int> tmp;
  swap(tmp, sub[root]);
  path.push_back(root);
  path.push_back(v);
  for (int u : tmp) {
    if (u == v) continue;
    int lca = query(root, u, v);
    path.push_back(lca);
    if (lca != u) {
      sub[lca].push_back(u);
    }
  }
  sort(path.begin(), path.end());
  path.erase(unique(path.begin(), path.end()), path.end());
  sort(path.begin(), path.end(), [&](int x, int y) {
    return query(root, x, y) == x;
  });
  auto answer = [&](int u, int v) {
    if (u > v) swap(u, v);
    Bridge(u, v);
  };
  for (int i = 0; i + 1 < path.size(); ++i) {
    answer(path[i], path[i + 1]);
  }
  for (int u : path)
    dfs(u);
}

void Solve(int _N) {
  n = _N;
  for (int i = 1; i < n; ++i)
    sub[0].push_back(i);
  dfs(0);
}

Compilation message (stderr)

meetings.cpp: In function 'void dfs(int)':
meetings.cpp:155:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  155 |   for (int i = 0; i + 1 < path.size(); ++i) {
      |                   ~~~~~~^~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 10 / 10
• Subtask 3: 12 / 12
• Subtask 4: 71 / 71