Submission #1156119

#	Time	Username	Problem	Language	Result	Execution time	Memory
1156119		motion	Valley (BOI19_valley)	C++20	23 / 100	136 ms	42072 KiB

valley

#include <bits/stdc++.h>
using namespace std;
#define ll long long
int n;
vector<bool> shop;
vector<ll> dep,magic;
vector<int> parents,dist,tin,tout;
vector<vector<pair<int,int>>> graf;
int tim=0;
void dfs(int x,int parent=-1,ll deph=0,int dista=0)
{
    tin[x]=++tim;
    parents[x]=parent;
    dep[x]=deph;
    dist[x]=dista;
    for(auto [node,l]:graf[x])
    {
        if(node==parent) continue;
        dfs(node,x,deph+l,dista+1);
    }
    if(shop[x])
    {
        magic[x]=dep[x];
    }
    else magic[x]=1e17;
    for(auto [node,l]:graf[x])
    {
        if(node==parent) continue;
        magic[x]=min(magic[x],magic[node]);
    }
    tout[x]=tim;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int s,q,e;
    cin>>n>>s>>q>>e;
    graf=vector<vector<pair<int,int>>>(n);
    magic=vector<ll>(n);
    vector<pair<int,int>> edges(n-1);
    int a,b,c;
    for(int i=0;i<n-1;i++)
    {
        cin>>a>>b>>c;
        graf[--a].push_back({--b,c});
        graf[b].push_back({a,c});
        edges[i]={a,b};
    }
    dep=vector<ll>(n,0);
    shop=vector<bool>(n,0);
    parents=vector<int>(n);
    dist=vector<int>(n);
    for(int i=0;i<s;i++)
    {
        cin>>a;
        shop[--a]=1;
    }
    tin=vector<int>(n);
    tout=vector<int>(n);
    dfs(--e);
    vector<vector<int>> logdist(n,vector<int>(log2(n)+1,-1));
    vector<vector<ll>> magicdist(n,vector<ll>(log2(n)+1,1e17));
    for(int i=0;i<n;i++)
    {
        if(magic[i]==1e17) continue;
        magic[i]-=dep[i]*2;
    }
    for(int i=0;i<n;i++)
    {
        logdist[i][0]=parents[i];
        magicdist[i][0]=magic[i];
    }
    for(int i=1;i<=log2(n);i++)
    {
        for(int j=0;j<n;j++)
        {
            int half=logdist[j][i-1];
            if(half==-1)
            {
                logdist[j][i]=-1;
                continue;
            }
            else
            {
                logdist[j][i]=logdist[half][i-1];
                magicdist[j][i]=min(magicdist[j][i-1],magicdist[half][i-1]);
            }
        }
    }
    int I,R;
    int i1,i2;
    for(int i=0;i<q;i++)
    {
        cin>>I>>R;
        I--;
        R--;
        if(dist[edges[I].first]<dist[edges[I].second])
        {
            i1=edges[I].second;
            i2=edges[I].first;
        }
        else
        {i1=edges[I].first;
        i2=edges[I].second;}
        if(tin[i1]>tin[R] || tout[i1]<tout[R])
        {
            cout<<"escaped\n";
            continue;
        }
        ll ans=dep[R];
        ll magi=magic[R];
        int k=dist[R]-dist[i2];
        for(int j=0;j<=log(n);j++)
        {
            if(k&(1<<j))
            {
                magi=min(magi,magicdist[R][j]);
                R=logdist[R][j];
            }
        }
        if(magi==1e17) cout<<"oo\n";
        else cout<<magi+ans<<'\n';



    }



}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 27
• Subtask 3: 23 / 23
• Subtask 4: 0 / 41