Submission #1208527

#	Time	Username	Problem	Language	Result	Execution time	Memory
1208527		k1r1t0	Fun Tour (APIO20_fun)	C++20	0 / 100	0 ms	332 KiB

fun

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int hoursRequired(int X, int Y);

int attractionsBehind(int X, int Y);

namespace k1r1t0 {
	const int N = 110000;

	bool used[N];
	int n, d[N], ds[N][2];
	vector<int> v[3];
	
	vector<int> createFunTour(int N, int Q) {
		n = N;
		array<int, 2> mn = {n, 0};
		for (int i = 1; i < n; i++) {
			int sz = attractionsBehind(0, i);
			if (sz >= n / 2) mn = min(mn, {sz, i});
		}
		int r = mn[1];
		for (int i = 0; i < n; i++)
			d[i] = hoursRequired(r, i);
		vector<int> sub;
		for (int i = 0; i < n; i++)
			if (d[i] == 1)
				sub.push_back(i);
		int cnt = (int) sub.size();
		for (int i = 0; i < cnt - 1; i++)
			for (int j = 0; j < n; j++)
				ds[j][i] = hoursRequired(sub[i], j);
		for (int i = 0; i < n; i++) {
			if (i == r) continue;
			int t = cnt - 1;
			for (int j = 0; j < cnt - 1; j++)
				if (ds[i][j] + 1 == d[i])
					t = j;
			v[t].push_back(i);
		}
		if (cnt == 1) {
			assert(n == 2);
			return {0, 1};
		}
		int sm = 0;
		for (int i = 1; i <= 2; i++)
			if (v[sm].size() > v[i].size())
				sm = i;
		v[sm].push_back(r);
		for (int k = 0; k < 3; k++)
			sort(begin(v[k]), end(v[k]), [&](int i, int j) {return d[i] < d[j];});
		vector<int> ans;
		int t = 0;
		for (int i = 1; i <= 2; i++)
			if (d[v[i].back()] > d[v[t].back()])
				t = i;
		for (int i = 0; i < n; i++) {
			int j = (t + 1) % 3;
			int k = (t + 2) % 3;
			int a = v[t].size();
			int b = v[j].size();
			int c = v[k].size();
			if (b > c) {
				swap(j, k);
				swap(b, c);
			}
			if (a - 1 + b < c && b != 0) {
				vector<int> na;
				na = v[j];
				na.insert(na.end(), v[t].begin(), v[t].end());
				v[t] = na;
				ans.push_back(v[t].back());
				v[t].pop_back();
				sort(begin(v[t]), end(v[t]), [&](int i, int j) {return d[i] < d[j];});
				t = k;
			} else {
				ans.push_back(v[t].back());
				v[t].pop_back();
				if (v[j].empty()) t = k;
				else if (v[k].empty()) t = j;
				else {
					if (d[v[j].back()] > d[v[k].back()]) t = j;
					else t = k;
				}
			}
		}
		return ans;
	}
};

vector<int> createFunTour(int N, int Q) {
	return k1r1t0::createFunTour(N, Q);
}

/*
#include <cassert>
#include <cstdio>

#include <algorithm>
#include <string>
#include <vector>

static void wrongAnswer(std::string message) {
  printf("WA: %s\n", message.c_str());
  exit(0);
}

namespace tree_helper {

static int N;
static int logN;
static std::vector<std::vector<int>> parent;
static std::vector<int> depth;
static std::vector<int> subtree_size;

static void dfs(
    const std::vector<std::vector<int>>& adj_list,
    int current_node, int parent_node) {
  parent[0][current_node] = parent_node;
  subtree_size[current_node] = 1;
  for (int i = 0; i < static_cast<int>(adj_list[current_node].size()); ++i) {
    const int next_node = adj_list[current_node][i];
    if (next_node != parent_node) {
      depth[next_node] = depth[current_node] + 1;
      dfs(adj_list, next_node, current_node);
      subtree_size[current_node] += subtree_size[next_node];
    }
  }
}

static void initializeTree(const std::vector<std::vector<int>>& adj_list) {
  N = static_cast<int>(adj_list.size());

  depth = std::vector<int>(N, 0);
  subtree_size = std::vector<int>(N, 0);
  for (logN = 0; (1 << logN) < N; ++logN) {}
  parent = std::vector<std::vector<int>>(logN, std::vector<int>(N, 0));

  dfs(adj_list, 0, 0);
  for (int i = 1; i < logN; ++i) {
    for (int j = 0; j < N; ++j) {
      parent[i][j] = parent[i - 1][parent[i - 1][j]];
    }
  }
}

static int getLowestCommonAncestor(int X, int Y) {
  if (depth[X] < depth[Y]) {
    std::swap(X, Y);
  }
  for (int i = logN - 1; i >= 0; --i) {
    if (depth[parent[i][X]] >= depth[Y]) {
      X = parent[i][X];
    }
  }
  if (X == Y) {
    return X;
  }
  for (int i = logN - 1; i >= 0; --i) {
    if (parent[i][X] != parent[i][Y]) {
      X = parent[i][X];
      Y = parent[i][Y];
    }
  }
  return parent[0][X];
}

static int getDistance(int X, int Y) {
  return depth[X] + depth[Y] - 2 * depth[getLowestCommonAncestor(X, Y)];
}

static int attractionsBehind(int X, int Y) {
  if (X == Y) {
    return N;
  }
  for (int i = logN - 1; i >= 0; --i) {
    if (depth[parent[i][X]] > depth[Y]) {
      X = parent[i][X];
    }
  }
  if (Y == parent[0][X]) {
    return N - subtree_size[X];
  }
  return subtree_size[Y];
}

static void checkFunTour(const std::vector<int>& fun_tour) {
  if (static_cast<int>(fun_tour.size()) != N) {
    wrongAnswer("Invalid size");
  }

  std::vector<bool> visited_attractions(N, false);
  for (int i = 0; i < N; ++i) {
    if (fun_tour[i] < 0 || fun_tour[i] >= N) {
      wrongAnswer("Invalid index");
    }
    if (visited_attractions[fun_tour[i]]) {
      wrongAnswer("Repeated index");
    }
    visited_attractions[fun_tour[i]] = true;
  }

  int last_travel_time = getDistance(fun_tour[0], fun_tour[1]);
  for (int i = 2; i < N; ++i) {
    int travel_time = getDistance(fun_tour[i - 1], fun_tour[i]);
    if (travel_time > last_travel_time) {
      wrongAnswer("Tour is not fun");
    }
    last_travel_time = travel_time;
  }
}

}  // namespace tree_helper

static int N, Q;

int hoursRequired(int X, int Y) {
  if (--Q < 0) {
    wrongAnswer("Too many queries");
  }
  if (X < 0 || X >= N || Y < 0 || Y >= N) {
    wrongAnswer("Invalid index");
  }
  return tree_helper::getDistance(X, Y);
}

int attractionsBehind(int X, int Y) {
  if (--Q < 0) {
    wrongAnswer("Too many queries");
  }
  if (X < 0 || X >= N || Y < 0 || Y >= N) {
    wrongAnswer("Invalid index");
  }
  return tree_helper::attractionsBehind(X, Y);
}

int main() {
  assert(2 == scanf("%d %d", &N, &Q));

  std::vector<std::vector<int>> adj_list(N);
  for (int i = 0; i < N - 1; ++i) {
    int A, B;
    assert(2 == scanf("%d %d", &A, &B));
    adj_list[A].push_back(B);
    adj_list[B].push_back(A);
  }
  tree_helper::initializeTree(adj_list);

  std::vector<int> fun_tour = createFunTour(N, Q);
  tree_helper::checkFunTour(fun_tour);

  for (int i = 0; i < N; ++i) {
    printf("%d%c", fun_tour[i], " \n"[i == N - 1]);
  }
  return 0;
}
//*/

• Subtask 1: 0 / 10
• Subtask 2: 0 / 16
• Subtask 3: 0 / 21
• Subtask 4: 0 / 19
• Subtask 5: 0 / 34