Submission #655240

#	Time	Username	Problem	Language	Result	Execution time	Memory
655240		inksamurai	Valley (BOI19_valley)	C++17	100 / 100	282 ms	70984 KiB

valley

#include <bits/stdc++.h>
#define int ll
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define rng(i,c,n) for(int i=c;i<n;i++)
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define vec(...) vector<__VA_ARGS__>
#define _3U2xVYR ios::sync_with_stdio(0),cin.tie(0)
typedef long long ll;
using pii=pair<int,int>;
using vi=vector<int>;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}

const int inf=1e17;

struct E{
	int to,w,id;
	E(int _to=0,int _w=0,int _id=0):
	to(_to),
	w(_w),
	id(_id){}
};

void chmin(int&a,int b){
	a=min(a,b);
}

signed main(){
_3U2xVYR;
	int n,k,q,rt;
	cin>>n>>k>>q>>rt;
	rt-=1;
	vec(pii) es;
	vec(vec(E)) adj(n);
	rep(i,n-1){
		int u,v,w;
		cin>>u>>v>>w;
		u-=1,v-=1;
		es.pb(pii(u,v));
		adj[u].pb(E(v,w,i));
		adj[v].pb(E(u,w,i));
	}
	vi rbe(n);
	rep(i,k){
		int v;
		cin>>v;
		v-=1;
		rbe[v]=1;
	}
	vec(vec(pii)) qry(n);
	rep(_,q){
		int id,v;
		cin>>id>>v;
		id-=1,v-=1;
		qry[v].pb(pii(id,_));
	}
	
	vi par(n,rt);
	vi dpth(n,0);
	vi qs(n,inf);
	auto dfs=[&](auto self,int v)->void{
		if(rbe[v]) qs[v]=dpth[v];
		for(auto [to,w,id]:adj[v]){
			if(to==par[v]) continue;
			par[to]=v;
			dpth[to]=dpth[v]+w;
			self(self,to);
			chmin(qs[v],qs[to]);
		}
	};
	dpth[rt]=0;
	dfs(dfs,rt);
	
	vec(vi) spr(20,vi(n,rt)); // everyone goes to rt
	vec(vi) dp(20,vi(n,inf));
	rep(i,n){
		spr[0][i]=par[i];
		chmin(dp[0][i],qs[i]-2*dpth[i]);
		chmin(dp[0][i],qs[par[i]]-2*dpth[par[i]]);
	}
	rng(j,1,20){
		rep(i,n){
			int up=spr[j-1][i];
			spr[j][i]=spr[j-1][up];
			chmin(dp[j][i],dp[j-1][i]);
			chmin(dp[j][i],dp[j-1][up]);
		}
	}

	auto eval=[&](int s,int v)->int{
		int res=inf;
		per(j,20){
			int up=spr[j][v];
			if(dpth[up]>dpth[s]){
				// print("go",up);
				chmin(res,dp[j][v]);
				v=up;
			}
		}
		return res;
	};

	vi pns(q,inf);
	set<int> st;
	auto rfs=[&](auto self,int v)->void{
		for(auto p:qry[v]){
			int id=p.fi;
			// print(id,v);
			if(st.find(id)==st.end()){
				pns[p.se]=-1;
			}else{
				int s=es[id].fi;
				if(dpth[s]>dpth[es[id].se]){
					s=es[id].se;
				}
				pns[p.se]=eval(s,v); // don't forget pencakes
				pns[p.se]+=dpth[v];
				// print(qs[v]);
				chmin(pns[p.se],qs[v]-dpth[v]);
			}
		}
		for(auto [to,w,id]:adj[v]){
			if(to==par[v]) continue;
			st.insert(id);
			self(self,to);
			st.erase(st.find(id));
		}
	};
	rfs(rfs,rt);

	rep(i,q){
		int ans=pns[i];
		if(ans<0){
			cout<<"escaped\n";
		}else if(ans>1e14){
			cout<<"oo\n";
		}else{
			cout<<ans<<"\n";
		}
	}
}

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41