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Submission #198797

# Submission time Handle Problem Language Result Execution time Memory
198797 2020-01-27T17:26:17 Z arnold518 Islands (IOI08_islands) C++14
100 / 100
 959 ms 130648 KB 
#include <bits/stdc++.h>
using namespace std;

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

const int MAXN = 1e6;

int N;
vector<pii> adj[MAXN+1];
pii to[MAXN+1];
ll ans, val;

bool vis[MAXN+1];

ll dfs(int now, ll dep)
{
	vis[now]=true;
	ll ret=dep;

	ll ta=0, tb=0;

	for(auto nxt : adj[now])
	{
		if(vis[nxt.first]) continue;
		ll p=dfs(nxt.first, dep+nxt.second);
		ret=max(ret, p);
		if(p>ta) tb=ta, ta=p;
		else if(p>tb) tb=p;
	}
	val=max(val, ta+tb-dep-dep);
	return ret;
}

int main()
{
	int i, j;

	scanf("%d", &N);
	for(i=1; i<=N; i++)
	{
		int u=i, v, w;
		scanf("%d%d", &v, &w);
		to[u]={v, w};
		adj[v].push_back({u, w});
	}

	for(i=1; i<=N; i++)
	{
		if(vis[i]) continue;

		int now=i;
		vector<int> cyc;
		while(!vis[now])
		{
			cyc.push_back(now);
			vis[now]=1;
			now=to[now].first;
		}

		reverse(cyc.begin(), cyc.end());
		while(!cyc.empty() && cyc.back()!=now) vis[cyc.back()]=0, cyc.pop_back();
		reverse(cyc.begin(), cyc.end());

		vector<ll> A, D;
		ll s=0; val=0;

		D.push_back(0);
		for(auto it : cyc) A.push_back(dfs(it, 0));
		for(auto it : cyc) D.push_back(D.back()+to[it].second), s+=to[it].second;
		D.pop_back();

		ll t=-1e18;
		for(j=0; j<cyc.size(); j++)
		{
			if(j) val=max(val, D[j]+A[j]+t);
			t=max(t, A[j]-D[j]);
		}

		t=-1e18;
		for(j=0; j<cyc.size(); j++)
		{
			if(j) val=max(val, s-D[j]+A[j]+t);
			t=max(t, D[j]+A[j]);
		}

		ans+=val;
	}
	printf("%lld", ans);
}

Compilation message

islands.cpp: In function 'int main()':
islands.cpp:75:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(j=0; j<cyc.size(); j++)
            ~^~~~~~~~~~~
islands.cpp:82:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(j=0; j<cyc.size(); j++)
            ~^~~~~~~~~~~
islands.cpp:40:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &N);
  ~~~~~^~~~~~~~~~
islands.cpp:44:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &v, &w);
   ~~~~~^~~~~~~~~~~~~~~~

Subtask #1
33.0 / 33.0

# Verdict Execution time Memory Grader output
1 Correct 21 ms 23800 KB Output is correct
2 Correct 21 ms 23672 KB Output is correct
3 Correct 20 ms 23800 KB Output is correct
4 Correct 20 ms 23800 KB Output is correct
5 Correct 20 ms 23800 KB Output is correct
6 Correct 20 ms 23800 KB Output is correct
7 Correct 21 ms 23800 KB Output is correct
8 Correct 20 ms 23800 KB Output is correct
9 Correct 21 ms 23800 KB Output is correct
10 Correct 22 ms 23804 KB Output is correct
11 Correct 40 ms 23800 KB Output is correct

Subtask #2
3.0 / 3.0

# Verdict Execution time Memory Grader output
1 Correct 20 ms 23800 KB Output is correct
2 Correct 21 ms 23800 KB Output is correct

Subtask #3
4.0 / 4.0

# Verdict Execution time Memory Grader output
1 Correct 21 ms 23800 KB Output is correct
2 Correct 23 ms 23928 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 28 ms 24292 KB Output is correct
2 Correct 37 ms 25080 KB Output is correct
3 Correct 30 ms 24440 KB Output is correct
4 Correct 25 ms 24056 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 44 ms 25720 KB Output is correct
2 Correct 59 ms 27440 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 102 ms 30196 KB Output is correct
2 Correct 103 ms 35184 KB Output is correct
3 Correct 133 ms 35564 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 172 ms 36684 KB Output is correct
2 Correct 207 ms 42212 KB Output is correct
3 Correct 220 ms 54604 KB Output is correct
4 Correct 295 ms 52316 KB Output is correct

Subtask #8
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 330 ms 40528 KB Output is correct
2 Correct 695 ms 65724 KB Output is correct
3 Correct 320 ms 46848 KB Output is correct
4 Correct 397 ms 60772 KB Output is correct
5 Correct 394 ms 59112 KB Output is correct
6 Correct 918 ms 52860 KB Output is correct
7 Correct 442 ms 70340 KB Output is correct

Subtask #9
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 485 ms 130648 KB Output is correct
2 Correct 476 ms 95480 KB Output is correct
3 Correct 454 ms 88016 KB Output is correct
4 Correct 564 ms 64112 KB Output is correct
5 Correct 399 ms 58716 KB Output is correct
6 Correct 395 ms 57836 KB Output is correct
7 Correct 959 ms 53500 KB Output is correct