Submission #366551

#	Time	Username	Problem	Language	Result	Execution time	Memory
366551		YJU	Beads and wires (APIO14_beads)	C++14	100 / 100	466 ms	46940 KiB

beads

#include<bits/stdc++.h>
#pragma GCC optimize("unroll-loops,no-stack-protector,Ofast")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
const ll MOD=1e9+7;
const ll MOD2=998244353;
const ll N=2e5+5;
const ld pi=acos(-1);
const ll INF=(1LL<<60);
#define SQ(i) ((i)*(i))
#define REP(i,n) for(ll i=0;i<n;i++)
#define REP1(i,n) for(ll i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define setp setprecision
#define lwb lower_bound
#define SZ(_a) (ll)_a.size()

vector<pll> v[N];
ll n,x,y,c,ans;
multiset<ll,greater<ll> > ms[N];
ll pac[N],dp[N],sum[N];

void DFS(ll nd,ll pa){
	for(auto i:v[nd]){
		if(i.X!=pa){
			pac[i.X]=i.Y;
			DFS(i.X,nd);
			sum[nd]+=dp[i.X];
			ms[nd].insert(sum[i.X]-dp[i.X]+i.Y);
		}
	}
	dp[nd]=max(sum[nd],(SZ(ms[nd])>0?sum[nd]+*ms[nd].begin()+pac[nd]:0LL));
}

void move(ll rt,ll to,ll ed){
	//remove
	sum[rt]-=dp[to];
	ms[rt].erase(ms[rt].find(sum[to]-dp[to]+ed));
	pac[rt]=ed;
	dp[rt]=max(sum[rt],(SZ(ms[rt])>0?sum[rt]+*ms[rt].begin()+pac[rt]:0LL));
	
	sum[to]+=dp[rt];
	pac[to]=0;
	ms[to].insert(sum[rt]-dp[rt]+ed);
	dp[to]=max(sum[to],(SZ(ms[to])>0?sum[to]+*ms[to].begin()+pac[to]:0LL));
}

void reroot(ll nd,ll pa){
	ans=max(ans,sum[nd]);
	for(auto i:v[nd]){
		if(i.X==pa)continue;
		move(nd,i.X,i.Y);
		reroot(i.X,nd);
		move(i.X,nd,i.Y);
	}
}

int main(){
	ios_base::sync_with_stdio(0);cin.tie(0);
	cin>>n;
	REP1(i,n-1){
		cin>>x>>y>>c;
		v[x].pb(mp(y,c));
		v[y].pb(mp(x,c));
	}
	DFS(1,0);
	reroot(1,0);
	cout<<ans<<"\n";
	return 0;
}
/*
10
4 10 2
1 2 21
1 3 13
6 7 1
7 9 5
2 4 3
2 5 8
1 6 55
6 8 34
*/

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43