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Submission #151531

# Submission time Handle Problem Language Result Execution time Memory
151531 2019-09-03T13:51:08 Z luciocf Islands (IOI08_islands) C++14
90 / 100
 1625 ms 131076 KB 
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

const int maxn = 1e6+10;
const ll inf = 1e18+10;

int n;

int peso[maxn];

int firstCycle, lastCycle, backEdge;
int pai[maxn], indCycle[maxn], edgePai[maxn];

ll dist[maxn], pref[maxn];
ll maiorDist[maxn], maiorDist2;
int indDist;

bool mark[maxn], markCycle[maxn];

vector<pii> grafo[maxn];

void findCycle(int u, int p)
{
	mark[u] = 1;

	for (auto pp: grafo[u])
	{
		int v = pp.first, e = pp.second;
		if (e == p) continue;

		if (mark[v])
		{
			firstCycle = u, lastCycle = v;
			backEdge = peso[e];
			continue;
		}

		pai[v] = u, edgePai[v] = peso[e];
		findCycle(v, e);
	}
}

void dfs(int u, int p, int root)
{
	if (dist[u] >= maiorDist[root])
		indDist = u;

	maiorDist[root] = max(maiorDist[root], dist[u]);

	for (auto pp: grafo[u])
	{
		int v = pp.first, e = pp.second;
		if (v == p || markCycle[v]) continue;

		dist[v] = dist[u]+1ll*peso[e];
		dfs(v, u, root);
	}
}

void dfs2(int u, int p)
{
	maiorDist2 = max(maiorDist2, dist[u]);

	for (auto pp: grafo[u])
	{
		int v = pp.first, e = pp.second;
		if (v == p || markCycle[v]) continue;

		dist[v] = dist[u]+1ll*peso[e];
		dfs2(v, u);
	}
}

int main(void)
{
	scanf("%d", &n);

	for (int i = 1; i <= n; i++)
	{
		int u, w;
		scanf("%d %d", &u, &w);

		peso[i] = w;

		grafo[u].push_back({i, i});
		grafo[i].push_back({u, i});
	}

	ll ans = 0;

	for (int T = 1; T <= n; T++)
	{
		if (mark[T]) continue;

		findCycle(T, 0);

		int at = lastCycle;
		ll soma = backEdge;

		vector<int> ciclo;

		while (true)
		{
			ciclo.push_back(at);
			markCycle[at] = 1;

			if (at == firstCycle) break;

			soma += 1ll*edgePai[at];
			at = pai[at];
		}

		reverse(ciclo.begin(), ciclo.end());

		ll M = 0, diam = 0;

		for (int i = 0; i < ciclo.size(); i++)
		{
			int c = ciclo[i];

			if (i > 0)
				pref[i] = pref[i-1] + 1ll*edgePai[c];

			dfs(c, 0, c);

			dist[indDist] = maiorDist2 = 0;
			markCycle[c] = 0;

			dfs2(indDist, 0);
			markCycle[c] = 1;

			diam = max(diam, maiorDist2);
		}

		ll maxi = -inf;
		for (int i = 0; i < ciclo.size(); i++)
		{
			int u = ciclo[i];

			M = max(M, maiorDist[u]+pref[i] + maxi);

			maxi = max(maxi, maiorDist[u]-pref[i]);
		}

		maxi = -inf;
		for (int i = 0; i < ciclo.size(); i++)
		{
			int u = ciclo[i];

			M = max(M, maiorDist[u]-pref[i] + maxi + soma);

			maxi = max(maxi, maiorDist[u]+pref[i]);
		}

		ans += max(M, diam);
	}

	printf("%lld\n", ans);
}

Compilation message

islands.cpp: In function 'int main()':
islands.cpp:121:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < ciclo.size(); i++)
                   ~~^~~~~~~~~~~~~~
islands.cpp:140:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < ciclo.size(); i++)
                   ~~^~~~~~~~~~~~~~
islands.cpp:150:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < ciclo.size(); i++)
                   ~~^~~~~~~~~~~~~~
islands.cpp:80:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
islands.cpp:85:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &u, &w);
   ~~~~~^~~~~~~~~~~~~~~~~

Subtask #1
33.0 / 33.0

# Verdict Execution time Memory Grader output
1 Correct 24 ms 23800 KB Output is correct
2 Correct 24 ms 23928 KB Output is correct
3 Correct 24 ms 23928 KB Output is correct
4 Correct 29 ms 23928 KB Output is correct
5 Correct 28 ms 23800 KB Output is correct
6 Correct 24 ms 23928 KB Output is correct
7 Correct 23 ms 23800 KB Output is correct
8 Correct 24 ms 23872 KB Output is correct
9 Correct 24 ms 23800 KB Output is correct
10 Correct 23 ms 23928 KB Output is correct
11 Correct 24 ms 23928 KB Output is correct

Subtask #2
3.0 / 3.0

# Verdict Execution time Memory Grader output
1 Correct 23 ms 23928 KB Output is correct
2 Correct 25 ms 23900 KB Output is correct

Subtask #3
4.0 / 4.0

# Verdict Execution time Memory Grader output
1 Correct 24 ms 24056 KB Output is correct
2 Correct 26 ms 24384 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 33 ms 25208 KB Output is correct
2 Correct 48 ms 27696 KB Output is correct
3 Correct 39 ms 25592 KB Output is correct
4 Correct 37 ms 24764 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 55 ms 29176 KB Output is correct
2 Correct 72 ms 32676 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 135 ms 40840 KB Output is correct
2 Correct 138 ms 44468 KB Output is correct
3 Correct 173 ms 53220 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 222 ms 56148 KB Output is correct
2 Correct 280 ms 74932 KB Output is correct
3 Correct 296 ms 81524 KB Output is correct
4 Correct 373 ms 98788 KB Output is correct

Subtask #8
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 435 ms 86944 KB Output is correct
2 Correct 1012 ms 123452 KB Output is correct
3 Correct 416 ms 88440 KB Output is correct
4 Correct 539 ms 120256 KB Output is correct
5 Correct 526 ms 120820 KB Output is correct
6 Correct 1625 ms 96608 KB Output is correct
7 Correct 584 ms 131072 KB Output is correct

Subtask #9
0 / 10.0

# Verdict Execution time Memory Grader output
1 Runtime error 557 ms 131076 KB Execution killed with signal 9 (could be triggered by violating memory limits)
2 Halted 0 ms 0 KB -