Submission #118154

#	Time	Username	Problem	Language	Result	Execution time	Memory
118154		baluteshih	Islands (IOI08_islands)	C++14	80 / 100	1236 ms	131072 KiB

islands

#include <bits/stdc++.h>
#define jizz ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define pb push_back
#define ET cout << "\n"
#define MEM(i,j) memset(i,j,sizeof i)
#define F first
#define S second
#define MP make_pair
#define ALL(v) v.begin(),v.end()
#define DB(a,s,e) {for(int i=s;i<e;++i) cout << a[i] << " ";ET;}
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
 
vector<int> G[1000005];
vector<pll> cir;
vector<ll> sum;
deque<int> dq;
bitset<1000005> yc,vis;
ll M;
pii edge[1000005];
const ll INF=1e18;
 
bool dfs(int u,int f)
{
	int flag=0;
	vis[u]=1;
	for(int i:G[u])
		if(i!=f)
			if(!vis[i])
				if(dfs(i,i))
					flag=1,cir.back().S=edge[i].S;
				else;
			else if(!yc[u])
				flag=1,yc[i]=1,cir.pb(MP(i,edge[i].S));
	if(u!=f)
		if(!vis[edge[u].F])
			if(dfs(edge[u].F,u))
				flag=1,cir.back().S=edge[u].S;
			else;
		else if(!yc[u])
			flag=1,yc[edge[u].F]=1,cir.pb(MP(edge[u].F,edge[u].S));
	if(flag)
		if(yc[u]) flag=0;
		else cir.pb(MP(u,0)),yc[u]=1;
	return flag;
}
 
ll dfs2(int u)
{
	ll mx=0,sx=0;
	yc[u]=1;
	for(int i:G[u])
		if(!yc[i])
		{
			ll d=dfs2(i)+edge[i].S;
			if(d>mx) sx=mx,mx=d;
			else if(d>sx) sx=d;
		}
	if(!yc[edge[u].F])
	{
		ll d=dfs2(edge[u].F)+edge[u].S;
		if(d>mx) sx=mx,mx=d;
		else if(d>sx) sx=d;
	}
	M=max(M,sx+mx);
	vector<int>().swap(G[u]);
	return mx;
}
 
int main()
{
	int n;
	ll ans=0;
	scanf("%d",&n);
	for(int i=1;i<=n;++i)
	{
		scanf("%d%d",&edge[i].F,&edge[i].S);
		if(edge[i].F!=i) G[edge[i].F].pb(i);
	}
	for(int i=1;i<=n;++i)
		if(!vis[i])
		{
			vector<pll>().swap(cir),vector<ll>().swap(sum),M=0,dfs(i,-1);
			deque<int>().swap(dq);
			for(int j=0;j<cir.size();++j)
				cir[j].F=dfs2(cir[j].F);
			sum.resize(cir.size());
			if(cir.size()>1)
			{
				int n=cir.size();
				sum[0]=0,dq.pb(0);
				for(int j=1;j<2*n;++j)
				{
					while(dq.size()&&j-dq[0]>=n) dq.pop_front();
					sum[j%n]=sum[(j-1)%n]+cir[(j-1)%n].S,M=max(M,sum[j%n]+cir[j%n].F+cir[dq[0]%n].F-sum[dq[0]%n]);
					while(dq.size()&&cir[j%n].F-sum[j%n]>=cir[dq.back()%n].F-sum[dq.back()%n])
						dq.pop_back();
					dq.pb(j);
				}
			}
			ans+=M;
		}
	printf("%lld\n",ans);
}

Compilation message (stderr)

islands.cpp: In function 'bool dfs(int, int)':
islands.cpp:30:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   if(i!=f)
     ^
islands.cpp:37:4: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
  if(u!=f)
    ^
islands.cpp:44:4: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
  if(flag)
    ^
islands.cpp: In function 'int main()':
islands.cpp:87:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<cir.size();++j)
                ~^~~~~~~~~~~
islands.cpp:76:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
islands.cpp:79:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&edge[i].F,&edge[i].S);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 33 / 33
• Subtask 2: 3 / 3
• Subtask 3: 4 / 4
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10