Submission #118101

#	Time	Username	Problem	Language	Result	Execution time	Memory
118101		baluteshih	Islands (IOI08_islands)	C++14	70 / 100	695 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;

struct mode
{
	ll F,S,num;
};

vector<mode> G[1000005];
vector<pll> cir;
vector<ll> len;
bitset<1000005> yc;
ll M,dft,dfn[1000005];
const ll INF=1e18;

bool dfs(ll u,ll f)
{
	ll flag=0;
	dfn[u]=++dft;
	for(auto i:G[u])
		if(i.num!=f)
			if(!dfn[i.F])
				if(dfs(i.F,i.num))
					flag=1,len.pb(i.S);
				else;
			else if(dfn[i.F]<=dfn[u])
				flag=1,yc[i.F]=1,cir.pb(MP(i.F,0)),len.pb(i.S);
	if(flag)
		if(yc[u]) flag=0;
		else cir.pb(MP(u,0)),yc[u]=1;
	return flag;
}

ll dfs2(ll u)
{
	ll mx=0,sx=0;
	yc[u]=1;
	for(auto i:G[u])
		if(!yc[i.F])
		{
			ll d=dfs2(i.F)+i.S;
			if(d>mx) sx=mx,mx=d;
			else if(d>sx) sx=d;
		}
	M=max(M,sx+mx);
	return mx;
}

int main()
{jizz
	ll n,a,w,ans=0,sum;
	cin >> n;
	for(int i=1;i<=n;++i)
	{
		cin >> a >> w;
		G[i].pb(mode{a,w,i});
		if(a!=i) G[a].pb(mode{i,w,i});
	}
	for(int i=1;i<=n;++i)
		if(!dfn[i])
		{
			cir.clear(),len.clear(),M=0,dfs(i,-1);
			for(ll j=0;j<cir.size();++j)
				cir[j].S=dfs2(cir[j].F);
			if(cir.size()>1)
			{
				ll n=cir.size();
				deque<pll> dq;
				sum=0,dq.pb(MP(0,cir[0].S));
				for(ll j=0;j<n;++j)	
					cir.pb(cir[j]),len.pb(len[j]);
				for(ll j=1;j<cir.size();++j)
				{
					while(dq.size()&&j-dq[0].F>=n) dq.pop_front();
					sum+=len[j-1],M=max(M,sum+cir[j].S+dq[0].S);
					while(dq.size()&&cir[j].S-sum>=dq.back().S)
						dq.pop_back();
					dq.pb(MP(j,cir[j].S-sum));
				}
			}
			ans+=M;
		}
	cout << ans << "\n";
}

Compilation message (stderr)

islands.cpp: In function 'bool dfs(ll, ll)':
islands.cpp:33:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   if(i.num!=f)
     ^
islands.cpp:40:4: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
  if(flag)
    ^
islands.cpp: In function 'int main()':
islands.cpp:75:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(ll j=0;j<cir.size();++j)
               ~^~~~~~~~~~~
islands.cpp:84:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(ll j=1;j<cir.size();++j)
                ~^~~~~~~~~~~

• 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: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10