Submission #924368

#	Time	Username	Problem	Language	Result	Execution time	Memory
924368		Edu175	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	308 ms	60056 KiB

Main

#include <bits/stdc++.h>
#define pb push_back
#define fst first
#define snd second
#define fore(i,a,b) for(ll i=a,ggdem=b;i<ggdem;++i)
#define SZ(x) ((int)x.size())
#define ALL(x) x.begin(),x.end()
#define mset(a,v) memset((a),(v),sizeof(a))
#define FIN ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define imp(v) for(auto messi:v)cout<<messi<<" "; cout<<"\n"
using namespace std;
typedef long long ll;
typedef pair<ll,ll> ii;
const ll MAXN=2e5+5;

ll uf[MAXN],pa[MAXN];
ll uf_find(ll x){return uf[x]<0?x:uf[x]=uf_find(uf[x]);}
void uf_join(ll x, ll y){
	x=uf_find(x),y=uf_find(y);
	if(-uf[x]>-uf[y])swap(x,y);
	uf[x]+=uf[y];
	uf[y]=x;
}

ll dp[MAXN];
vector<ll>g[MAXN]; ll n;
const ll K=18; //K such that 2^K>=n
ll F[K][MAXN],D[MAXN];
void lca_dfs(ll x){
	for(auto y:g[x]){
		if(y==F[0][x])continue;
		F[0][y]=x;D[y]=D[x]+1;lca_dfs(y);
	}
}
void lca_init(){
	D[0]=0;F[0][0]=-1;
	lca_dfs(0);
	fore(k,1,K)fore(x,0,n){
		if(F[k-1][x]<0)F[k][x]=-1;
		else F[k][x]=F[k-1][F[k-1][x]];
	}
}
ll lca(ll x,ll y){
	if(D[x]<D[y])swap(x,y);
	for(ll k=K-1;k>=0;k--)if(D[x]-(1ll<<k)>=D[y])x=F[k][x];
	if(x==y)return x;
	for(ll k=K-1;k>=0;k--)if(F[k][x]!=F[k][y])x=F[k][x],y=F[k][y];
	return F[0][x];
}

ll dis(ll x, ll y){return D[x]+D[y]-2*D[lca(x,y)];}

int main(){FIN;
	cin>>n;
	vector<ll>a(n),p(n);
	fore(i,0,n)cin>>a[i],a[i]--,p[a[i]]=i;
	fore(i,0,n-1){
		ll u,v; cin>>u>>v; u--,v--;
		g[u].pb(v);
		g[v].pb(u);
	}
	mset(uf,-1);
	lca_init();
	fore(i,0,n){
		auto x=p[i];
		for(auto y:g[x])if(a[y]<a[x]){
			y=pa[uf_find(y)];
			dp[x]=max(dp[x],dp[y]+dis(x,y));
			uf_join(x,y);
		}
		pa[uf_find(x)]=x;
	}
	cout<<dp[p[n-1]]<<"\n";
	return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26