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답안 #151542

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
151542 2019-09-03T14:08:51 Z luciocf Islands (IOI08_islands) C++17
90 / 100
 1537 ms 131076 KB 
#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef pair<int, int> pii;
 
const int maxn = 1e6+1;
const ll inf = 1e18+10;
 
int n;
 
int peso[maxn];
 
int firstCycle, lastCycle, backEdge;
int pai[maxn], edgePai[maxn];
 
ll pref[maxn];
ll maiorDist[maxn], maiorDist2;
int indDist;
 
bitset<maxn> mark, markCycle;
 
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, ll dist)
{
	if (dist >= maiorDist[root])
		indDist = u;
 
	maiorDist[root] = max(maiorDist[root], dist);
 
	for (auto pp: grafo[u])
	{
		int v = pp.first, e = pp.second;
		if (v == p || markCycle[v]) continue;
 
		dfs(v, u, root, dist+1ll*peso[e]);
	}
}
 
void dfs2(int u, int p, ll dist)
{
	maiorDist2 = max(maiorDist2, dist);
 
	for (auto pp: grafo[u])
	{
		int v = pp.first, e = pp.second;
		if (v == p || markCycle[v]) continue;
 
		dfs2(v, u, dist+1ll*peso[e]);
	}
}
 
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;
	vector<int> ciclo;
 
	for (int T = 1; T <= n; T++)
	{
		if (mark[T]) continue;
 
		findCycle(T, 0);
 
		int at = lastCycle;
		ll soma = backEdge;
 
		ciclo.clear();
 
		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, 0);
 
			maiorDist2 = 0;
			markCycle[c] = 0;
 
			dfs2(indDist, 0, 0);
			markCycle[c] = 1;
 
			diam = max(diam, maiorDist2);
		}
 
		ll maxi1 = -inf, maxi2 = -inf;
		for (int i = 0; i < ciclo.size(); i++)
		{
			int u = ciclo[i];
 
			M = max(M, maiorDist[u]+pref[i] + maxi1);
			maxi1 = max(maxi1, maiorDist[u]-pref[i]);
 
			M = max(M, maiorDist[u]-pref[i] + maxi2 + soma);
 
			maxi2 = max(maxi2, maiorDist[u]+pref[i]);
		}
 
		ans += max(M, diam);
	}
 
	printf("%lld\n", ans);
}

Compilation message

islands.cpp: In function 'int main()':
islands.cpp:120:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < ciclo.size(); i++)
                   ~~^~~~~~~~~~~~~~
islands.cpp:139:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < ciclo.size(); i++)
                   ~~^~~~~~~~~~~~~~
islands.cpp:78:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
islands.cpp:83:8: 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

# 결과 실행 시간 메모리 Grader output
1 Correct 23 ms 23800 KB Output is correct
2 Correct 23 ms 23800 KB Output is correct
3 Correct 23 ms 23932 KB Output is correct
4 Correct 23 ms 23928 KB Output is correct
5 Correct 23 ms 23800 KB Output is correct
6 Correct 23 ms 23800 KB Output is correct
7 Correct 24 ms 23928 KB Output is correct
8 Correct 23 ms 23928 KB Output is correct
9 Correct 23 ms 23800 KB Output is correct
10 Correct 23 ms 23800 KB Output is correct
11 Correct 24 ms 23928 KB Output is correct

Subtask #2
3.0 / 3.0

# 결과 실행 시간 메모리 Grader output
1 Correct 24 ms 23928 KB Output is correct
2 Correct 23 ms 23928 KB Output is correct

Subtask #3
4.0 / 4.0

# 결과 실행 시간 메모리 Grader output
1 Correct 24 ms 23928 KB Output is correct
2 Correct 26 ms 24128 KB Output is correct

Subtask #4
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 33 ms 24824 KB Output is correct
2 Correct 47 ms 26872 KB Output is correct
3 Correct 45 ms 25080 KB Output is correct
4 Correct 31 ms 24440 KB Output is correct

Subtask #5
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 57 ms 28152 KB Output is correct
2 Correct 71 ms 30664 KB Output is correct

Subtask #6
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 131 ms 36432 KB Output is correct
2 Correct 136 ms 39708 KB Output is correct
3 Correct 166 ms 47148 KB Output is correct

Subtask #7
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 215 ms 47004 KB Output is correct
2 Correct 266 ms 64616 KB Output is correct
3 Correct 290 ms 69372 KB Output is correct
4 Correct 368 ms 83144 KB Output is correct

Subtask #8
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 426 ms 74836 KB Output is correct
2 Correct 958 ms 106684 KB Output is correct
3 Correct 421 ms 70140 KB Output is correct
4 Correct 540 ms 98656 KB Output is correct
5 Correct 535 ms 99412 KB Output is correct
6 Correct 1537 ms 72772 KB Output is correct
7 Correct 567 ms 116144 KB Output is correct

Subtask #9
0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Runtime error 583 ms 131076 KB Execution killed with signal 9 (could be triggered by violating memory limits)
2 Halted 0 ms 0 KB -