Submission #780805

#	Time	Username	Problem	Language	Result	Execution time	Memory
780805		Elias	Stations (IOI20_stations)	C++17	0 / 100	3029 ms	2097152 KiB

stations

#ifndef _DEBUG
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#endif

#include <bits/stdc++.h>

using namespace std;

#define all(x) (x).begin(), (x).end()

#ifndef _DEBUG
#include "stations.h"
#endif

#ifdef _DEBUG

std::vector<int> label(int n, int k, std::vector<int> u, std::vector<int> v);
int find_next_station(int s, int t, std::vector<int> c);

#endif

vector<int> l;
int timer;

vector<vector<int>> adj;

void dfs(int i, int p)
{
	if (p == -1 || l[p] == -1)
		l[i] = timer++;
	for (int c : adj[i])
		if (c != p)
			dfs(c, i);
	if (l[i] == -1)
		l[i] = timer++;
}

vector<int> label(int n, int k, std::vector<int> u, std::vector<int> v)
{
	timer = 0;
	l.resize(n, -1);
	adj.resize(n, {});

	for (int i = 0; i < n - 1; i++)
	{
		adj[u[i]].push_back(v[i]);
		adj[v[i]].push_back(u[i]);
	}

	dfs(0, -1);

	return l;
}

int find_next_station(int s, int t, std::vector<int> c)
{
	if (s > c.back())
	{ // is larger than all adjacent
		reverse(c.begin(), c.end());
		if (t > s)
			return c.back();

		for (int other : c)
		{
			if (t >= other)
				return other;
		}
		return c.back();
	}
	else
	{ // is smaller than all adjacent
		if (t < s)
			return c.back(); // is not in subtree, as s is the smallest in the subtree
		for (int other : c)
		{
			if (t <= other)
				return other;
		}
		return c.back();
	}
}

#ifdef _DEBUG

static int max_label = 0;
static int r, n, k, q;
static std::vector<int> u, v, labels, answers;
static std::map<int, int> reverse_labels;
static std::vector<std::vector<int>> adjlist;
static int s, t, w;
static std::vector<int> c;

int main()
{
	assert(scanf("%d", &r) == 1);
	for (int tc = 0; tc < r; tc++)
	{
		assert(scanf("%d%d", &n, &k) == 2);
		u.resize(n - 1);
		v.resize(n - 1);
		adjlist.clear();
		adjlist.resize(n);
		for (int i = 0; i < n - 1; i++)
		{
			assert(scanf("%d%d", &u[i], &v[i]) == 2);
			adjlist[u[i]].push_back(v[i]);
			adjlist[v[i]].push_back(u[i]);
		}
		labels = label(n, k, u, v);
		if ((int)labels.size() != n)
		{
			printf("Number of labels not equal to %d\n", n);
			exit(0);
		}
		reverse_labels.clear();
		for (int i = 0; i < n; i++)
		{
			if (labels[i] < 0 || labels[i] > k)
			{
				printf("Label not in range 0 to %d\n", k);
				exit(0);
			}
			if (reverse_labels.find(labels[i]) != reverse_labels.end())
			{
				printf("Labels not unique\n");
				exit(0);
			}
			reverse_labels[labels[i]] = i;
			if (labels[i] > max_label)
			{
				max_label = labels[i];
			}
		}
		assert(scanf("%d", &q) == 1);
		for (int i = 0; i < q; i++)
		{
			assert(scanf("%d%d%d", &s, &t, &w) == 3);
			c.clear();
			for (int v : adjlist[s])
			{
				c.push_back(labels[v]);
			}
			std::sort(c.begin(), c.end());
			int answer = find_next_station(labels[s], labels[t], c);
			if (!std::binary_search(c.begin(), c.end(), answer))
			{
				printf("Label %d returned by find_next_station not found in c\n", answer);
				exit(0);
			}
			answers.push_back(reverse_labels[answer]);
		}
	}
	printf("%d\n", max_label);
	for (int index : answers)
	{
		printf("%d\n", index);
	}
	exit(0);
}

#endif

• Subtask 1: 0 / 5
• Subtask 2: 0 / 8
• Subtask 3: 0 / 16
• Subtask 4: 0 / 10
• Subtask 5: 0 / 61