Submission #1133003

#	Time	Username	Problem	Language	Result	Execution time	Memory
1133003		aaa2312	Valley (BOI19_valley)	C++20	100 / 100	301 ms	71396 KiB

valley

#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

const ll mod = 1e9 + 7;
const ll mod2 = 998244353;
const ll max_dist=1e16;

ll gcd(ll a, ll b) {
    return b ? gcd(b, a % b) : a;
}

ll pow(ll a, ll b) {
    ll ans = 1;
    while (b) {
        if (b & 1) ans *= a;
        b >>= 1;
        a *= a;
    }
    return ans;
}

ll pow(ll a, ll b, ll c) {
    ll ans = 1;
    while (b) {
        if (b & 1) ans = (ans * a) % c;
        b >>= 1;
        a = (a * a) % c;
    }
    return ans;
}

void check(bool b) {
    if (b)
        cout << "Yes\n";
    else
        cout << "No\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    ll n,s,q,e;
    cin>>n>>s>>q>>e;
    vector<vector<pair<ll,ll>>> adj(n+1);
    vector<pair<ll,ll>>edges;
    for (int i = 0; i < n - 1; ++i) {
        ll u,v,w;
        cin>>u>>v>>w;
        edges.push_back({u,v});
        adj[u].push_back({v,w});
        adj[v].push_back({u,w});
    }
    vector<ll>par(n+1),dp(n+1,max_dist),par_dist(n+1),tin(n+1),tout(n+1);
    for (int i = 0; i < s; ++i) {
        ll x;
        cin>>x;
        dp[x]=0;
    }
    ll timer=0;
    function<void(ll,ll)>dfs=[&](ll u,ll p){
        tin[u]=++timer;
        par[u]=p;
        for(auto [v,w]:adj[u]){
            if(v==p)continue;
            par_dist[v]=w;
            dfs(v,u);
            dp[u]=min(dp[u],dp[v]+w);
        }
        tout[u]=++timer;
    };
    dfs(e,e);
    ll l=log2(n)+1;
    vector<vector<ll>>anc(n+1,vector<ll>(l)),min_anc(n+1,vector<ll>(l)),dist(n+1,vector<ll>(l));
    for (int i = 1; i <= n; ++i) {
        anc[i][0]=par[i];
        dist[i][0]=par_dist[i];
        min_anc[i][0]=min(par_dist[i]+dp[par[i]],dp[i]);
    }
    for (int j = 1; j < l; ++j) {
        for (int i = 1; i <= n; ++i) {
            anc[i][j]=anc[anc[i][j-1]][j-1];
            dist[i][j]=dist[i][j-1]+dist[anc[i][j-1]][j-1];
            min_anc[i][j]=min(min_anc[i][j-1],min_anc[anc[i][j-1]][j-1]+dist[i][j-1]);
        }
    }
    function<bool(ll,ll)>is_ancestor=[&](ll u,ll v){
        return tin[u]<=tin[v]&&tout[u]>=tout[v];
    };
    function<bool(ll,ll)>is_hard_ancestor=[&](ll u,ll v){
        return tin[u]<tin[v]&&tout[u]>tout[v];
    };
    while (q--){
        ll x,v;
        cin>>x>>v;--x;
        x=(is_ancestor(edges[x].first,edges[x].second)?edges[x].second:edges[x].first);
        if (!is_ancestor(x,v)){
            cout<<"escaped\n";
            continue;
        }
        ll ans=dp[v],z=0;
        for (int i = l-1; i >=0 ; --i) {
            if (!is_hard_ancestor(anc[v][i],x)){
                ans= min(ans,min_anc[v][i]+z);
                z+=dist[v][i];
                v=anc[v][i];
            }
        }
        if (ans==max_dist){
            cout<<"oo\n";
        } else
            cout<<ans<<'\n';
    }
    return 0;
}

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