Submission #867615

#	Time	Username	Problem	Language	Result	Execution time	Memory
867615		12345678	Valley (BOI19_valley)	C++17	100 / 100	160 ms	55892 KiB

valley

#include <bits/stdc++.h>

using namespace std;

#define ll long long

const int nx=1e5+5, kx=17;
ll n, s, q, e, u, v, w, mnd[nx], mn[nx][kx], pa[nx][kx], ans[nx], lvl[nx], dp[nx], qs[nx], x, y, cnt;
vector<tuple<ll, ll, ll>> d[nx];
vector<pair<ll, ll>> t[nx];
bool pw[nx];

void dfs(int u, int p)
{
    //cout<<"here"<<' '<<u<<' '<<mnd[u]<<'\n';
    pa[u][0]=p;
    lvl[u]=lvl[p]+1;
    for (int i=1; i<kx; i++) pa[u][i]=pa[pa[u][i-1]][i-1];
    for (auto [v, w, i]:d[u])
    {
        if (v==p) continue;
        qs[v]=qs[u]+w;
        dfs(v, u);
        mnd[u]=min(mnd[u], mnd[v]+w);
    }
    if (pw[u]) mnd[u]=0;
}

void dfs2(int u, int p)
{
    for (int i=1; i<kx; i++) mn[u][i]=min(mn[u][i-1], mn[pa[u][i-1]][i-1]+qs[u]-qs[pa[u][i-1]]);
    //for (int i=0; i<4; i++) cout<<u<<' '<<i<<' '<<mn[u][i]<<'\n';
    for (auto [x, y]:t[u]) 
    {
        if (dp[x])
        {
            ll dn=dp[x], res=mnd[u], tmp=u, vl=0;
            for (int i=kx-1; i>=0; i--) if (lvl[pa[tmp][i]]>=lvl[dn]) res=min(res, mn[tmp][i]+vl), vl+=qs[tmp]-qs[pa[tmp][i]], tmp=pa[tmp][i];
            ans[y]=res; 
        }
        else ans[y]=-1;
    }
    for (auto [v, w, i]:d[u])
    {
        if (v==p) continue;
        dp[i]=v;
        mn[v][0]=min(mnd[u]+w, (ll)1e18);
        dfs2(v, u);
        dp[i]=0;
    }
}

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin>>n>>s>>q>>e;
    for (int i=1; i<=n-1; i++) cin>>u>>v>>w, d[u].push_back({v, w, i}), d[v].push_back({u, w, i});
    for (int i=1; i<=n; i++) mnd[i]=1e18;
    for (int i=0; i<s; i++) cin>>x, pw[x]=1;
    for (int i=0; i<q; i++) cin>>x>>y, t[y].push_back({x, i});
    dfs(e, e);
    mn[e][0]=1e18;
    dfs2(e, e);
    for (int i=0; i<q; i++)
    {
        if (ans[i]==-1) cout<<"escaped\n";
        else if (ans[i]>=1e18) cout<<"oo\n";
        else cout<<ans[i]<<'\n';
    }
}

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