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Submission #379540

# Submission time Handle Problem Language Result Execution time Memory
379540 2021-03-18T13:38:32 Z peijar Olympic Bus (JOI20_ho_t4) C++17
37 / 100
 1000 ms 1948 KB 
#include <bits/stdc++.h>
using namespace std;

struct Arete
{
	int from, to, cost, costFlip;
};

const int MAXN = 200;
const int INF = 2e9;

vector<int> adj[MAXN];
vector<int> adjRev[MAXN];
vector<Arete> aretes;
int nbSommets, nbAretes;

// O(M log N)

vector<int> distances, pred;

pair<vector<int>, vector<int>> dijsktra(int from, bool flip=false)
{
	priority_queue<pair<int, int>> pq;
	pq.push({0, from});
	distances.assign(nbSommets, INF);
	pred.assign(nbSommets, -1);
	distances[from] = 0;
	while (!pq.empty())
	{
		auto [curDis, iNoeud] = pq.top(); pq.pop();
		curDis = -curDis;
		if (curDis > distances[iNoeud])
			continue;
		for (auto iArete : (flip ? adjRev[iNoeud] : adj[iNoeud]))
		{
			int iFrere = flip ? aretes[iArete].from : aretes[iArete].to;
			int nxtDis = curDis + aretes[iArete].cost;
			if (nxtDis < distances[iFrere])
			{
				pq.push({-nxtDis, iFrere});
				pred[iFrere] = iArete;
				distances[iFrere] = nxtDis;
			}
		}
	}
	return make_pair(distances, pred);
}

signed main(void)
{
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	
	cin >> nbSommets >> nbAretes;
	aretes.resize(nbAretes);
	for (auto &[from, to, cost, costFlip] : aretes)
	{
		cin >> from >> to >> cost >> costFlip;
		--from, --to;
	}
	for (int iArete = 0; iArete < nbAretes; ++iArete) 
	{
		adj[aretes[iArete].from].push_back(iArete);
		adjRev[aretes[iArete].to].push_back(iArete);
	}

	auto [distances0, pred0] = dijsktra(0);
	auto [distances0Rev, pred0Rev] = dijsktra(0, 1);
	auto [distances1, pred1] = dijsktra(nbSommets-1);
	auto [distances1Rev, pred1Rev] = dijsktra(nbSommets-1, 1);
	int curSol = INF;
	if (distances0[nbSommets-1] < INF and distances1[0] < INF)
		curSol = distances0[nbSommets-1] + distances1[0];
	vector<bool> aretesPrise(nbAretes);

	if (distances0[nbSommets-1] != INF)
	{
		int cur = nbSommets-1;
		while (cur)
		{
			assert(pred0[cur] != -1);
			aretesPrise[pred0[cur]] = true;
			cur = aretes[pred0[cur]].from;
		}
	}

	if (distances1[0] != INF)
	{
		int cur = 0;
		while (cur != nbSommets-1)
		{
			assert(pred1[cur] != -1);
			aretesPrise[pred1[cur]] = true;
			cur = aretes[pred1[cur]].from;
		}
	}

	// O(NM log N)
	
	for (int iArete = 0; iArete < nbAretes; ++iArete) 
		if (!aretesPrise[iArete])
		{
			int dis0 = distances0[nbSommets-1];
			int dis1 = distances1[0];;
			int iTo = aretes[iArete].to;
			int iFrom = aretes[iArete].from;
			if (distances0[iTo] < INF and distances1Rev[iFrom] < INF)
				dis0 = min(dis0, 
						distances0[aretes[iArete].to] + distances1Rev[aretes[iArete].from]
						+ aretes[iArete].cost);
			if (distances1[iTo] < INF and distances0Rev[iFrom] < INF)
				dis1 = min(dis1, 
						distances1[aretes[iArete].to] + distances0Rev[aretes[iArete].from]
						+ aretes[iArete].cost);
			if (dis0 < INF and dis1 < INF)
				curSol = min(curSol, dis0 + dis1 + aretes[iArete].costFlip);
		}

	for (int iArete = 0; iArete < nbAretes; ++iArete) 
		if (aretesPrise[iArete])
		{
			int iFrom = aretes[iArete].from;
			int iTo = aretes[iArete].to;
			int posFrom = lower_bound(adj[iFrom].begin(), adj[iFrom].end(), iArete)
				- adj[iFrom].begin();
			int posTo = lower_bound(adjRev[iTo].begin(), adjRev[iTo].end(), iArete)
				- adjRev[iTo].begin();
			swap(aretes[iArete].from, aretes[iArete].to);
			swap(adj[iFrom][posFrom], adj[iFrom].back());
			swap(adjRev[iTo][posTo], adjRev[iTo].back());
			adj[iFrom].pop_back();
			adjRev[iTo].pop_back();
			adjRev[iFrom].push_back(iArete);
			adj[iTo].push_back(iArete);

			auto [dis0, p0] = dijsktra(0);
			auto [dis1, p1]= dijsktra(nbSommets-1);

			if (dis1[0] < INF and dis0[nbSommets-1] < INF)
				curSol = min(curSol, dis0[nbSommets-1] + dis1[0] + aretes[iArete].costFlip);

			adj[iTo].pop_back();
			adjRev[iFrom].pop_back();
			adj[iFrom].push_back(iArete);
			adjRev[iTo].push_back(iArete);
			swap(adj[iFrom][posFrom], adj[iFrom].back());
			swap(adjRev[iTo][posTo], adjRev[iTo].back());
			swap(aretes[iArete].from, aretes[iArete].to);
		}

	if (curSol == INF)
		curSol = -1;
	cout << curSol << endl;
}

Subtask #1
5.0 / 5.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 364 KB Output is correct
2 Correct 1 ms 364 KB Output is correct
3 Correct 2 ms 364 KB Output is correct
4 Correct 2 ms 364 KB Output is correct
5 Correct 1 ms 364 KB Output is correct
6 Correct 1 ms 364 KB Output is correct
7 Correct 1 ms 364 KB Output is correct
8 Correct 1 ms 364 KB Output is correct
9 Correct 1 ms 364 KB Output is correct
10 Correct 20 ms 364 KB Output is correct
11 Correct 25 ms 384 KB Output is correct
12 Correct 26 ms 364 KB Output is correct
13 Correct 1 ms 364 KB Output is correct
14 Correct 2 ms 364 KB Output is correct
15 Correct 1 ms 364 KB Output is correct
16 Correct 2 ms 364 KB Output is correct

Subtask #2
11.0 / 11.0

# Verdict Execution time Memory Grader output
1 Correct 26 ms 1772 KB Output is correct
2 Correct 27 ms 1900 KB Output is correct
3 Correct 27 ms 1900 KB Output is correct
4 Correct 2 ms 364 KB Output is correct
5 Correct 2 ms 364 KB Output is correct
6 Correct 1 ms 364 KB Output is correct
7 Correct 1 ms 364 KB Output is correct
8 Correct 0 ms 364 KB Output is correct
9 Correct 23 ms 1772 KB Output is correct
10 Correct 23 ms 1772 KB Output is correct
11 Correct 28 ms 1900 KB Output is correct
12 Correct 27 ms 1772 KB Output is correct
13 Correct 26 ms 1772 KB Output is correct
14 Correct 27 ms 1900 KB Output is correct

Subtask #3
21.0 / 21.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 364 KB Output is correct
2 Correct 1 ms 364 KB Output is correct
3 Correct 19 ms 1388 KB Output is correct
4 Correct 1 ms 364 KB Output is correct
5 Correct 22 ms 1900 KB Output is correct
6 Correct 0 ms 364 KB Output is correct
7 Correct 1 ms 364 KB Output is correct
8 Correct 20 ms 1772 KB Output is correct
9 Correct 20 ms 1792 KB Output is correct
10 Correct 21 ms 1772 KB Output is correct
11 Correct 21 ms 1772 KB Output is correct
12 Correct 21 ms 1900 KB Output is correct
13 Correct 1 ms 364 KB Output is correct
14 Correct 1 ms 364 KB Output is correct
15 Correct 1 ms 364 KB Output is correct
16 Correct 0 ms 364 KB Output is correct
17 Correct 1 ms 364 KB Output is correct
18 Correct 1 ms 364 KB Output is correct
19 Correct 21 ms 1920 KB Output is correct
20 Correct 21 ms 1900 KB Output is correct
21 Correct 24 ms 1772 KB Output is correct
22 Correct 21 ms 1772 KB Output is correct

Subtask #4
0 / 63.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 364 KB Output is correct
2 Correct 1 ms 364 KB Output is correct
3 Correct 2 ms 364 KB Output is correct
4 Correct 2 ms 364 KB Output is correct
5 Correct 1 ms 364 KB Output is correct
6 Correct 1 ms 364 KB Output is correct
7 Correct 1 ms 364 KB Output is correct
8 Correct 1 ms 364 KB Output is correct
9 Correct 1 ms 364 KB Output is correct
10 Correct 20 ms 364 KB Output is correct
11 Correct 25 ms 384 KB Output is correct
12 Correct 26 ms 364 KB Output is correct
13 Correct 1 ms 364 KB Output is correct
14 Correct 2 ms 364 KB Output is correct
15 Correct 1 ms 364 KB Output is correct
16 Correct 2 ms 364 KB Output is correct
17 Correct 26 ms 1772 KB Output is correct
18 Correct 27 ms 1900 KB Output is correct
19 Correct 27 ms 1900 KB Output is correct
20 Correct 2 ms 364 KB Output is correct
21 Correct 2 ms 364 KB Output is correct
22 Correct 1 ms 364 KB Output is correct
23 Correct 1 ms 364 KB Output is correct
24 Correct 0 ms 364 KB Output is correct
25 Correct 23 ms 1772 KB Output is correct
26 Correct 23 ms 1772 KB Output is correct
27 Correct 28 ms 1900 KB Output is correct
28 Correct 27 ms 1772 KB Output is correct
29 Correct 26 ms 1772 KB Output is correct
30 Correct 27 ms 1900 KB Output is correct
31 Correct 3 ms 364 KB Output is correct
32 Correct 1 ms 364 KB Output is correct
33 Correct 19 ms 1388 KB Output is correct
34 Correct 1 ms 364 KB Output is correct
35 Correct 22 ms 1900 KB Output is correct
36 Correct 0 ms 364 KB Output is correct
37 Correct 1 ms 364 KB Output is correct
38 Correct 20 ms 1772 KB Output is correct
39 Correct 20 ms 1792 KB Output is correct
40 Correct 21 ms 1772 KB Output is correct
41 Correct 21 ms 1772 KB Output is correct
42 Correct 21 ms 1900 KB Output is correct
43 Correct 1 ms 364 KB Output is correct
44 Correct 1 ms 364 KB Output is correct
45 Correct 1 ms 364 KB Output is correct
46 Correct 0 ms 364 KB Output is correct
47 Correct 1 ms 364 KB Output is correct
48 Correct 1 ms 364 KB Output is correct
49 Correct 21 ms 1920 KB Output is correct
50 Correct 21 ms 1900 KB Output is correct
51 Correct 24 ms 1772 KB Output is correct
52 Correct 21 ms 1772 KB Output is correct
53 Correct 32 ms 1772 KB Output is correct
54 Correct 31 ms 1772 KB Output is correct
55 Correct 29 ms 1772 KB Output is correct
56 Correct 2 ms 364 KB Output is correct
57 Correct 2 ms 364 KB Output is correct
58 Correct 128 ms 1516 KB Output is correct
59 Correct 153 ms 1532 KB Output is correct
60 Correct 206 ms 1644 KB Output is correct
61 Correct 127 ms 1644 KB Output is correct
62 Correct 145 ms 1536 KB Output is correct
63 Correct 203 ms 1644 KB Output is correct
64 Correct 747 ms 1948 KB Output is correct
65 Correct 797 ms 1872 KB Output is correct
66 Execution timed out 1042 ms 1868 KB Time limit exceeded
67 Halted 0 ms 0 KB -