Submission #1147165

#	Time	Username	Problem	Language	Result	Execution time	Memory
1147165		Nelt	Valley (BOI19_valley)	C++20	100 / 100	173 ms	26676 KiB

valley

#include <bits/stdc++.h>
#define ll long long
#define endl "\n"
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll N = 1e5 + 5;
ll st[N << 2];
void build(ll l, ll r, ll v)
{
    if (l == r)
    {
        st[v] = 1e18;
        return;
    }
    ll mid = (l + r) >> 1;
    build(l, mid, v << 1);
    build(mid + 1, r, v << 1 | 1);
    st[v] = 1e18;
}
void modify(ll i, ll j, ll x, ll l, ll r, ll v)
{
    if (max(i, l) > min(j, r))
        return;
    if (i <= l and r <= j)
    {
        st[v] = min(st[v], x);
        return;
    }
    ll mid = (l + r) >> 1;
    modify(i, j, x, l, mid, v << 1);
    modify(i, j, x, mid + 1, r, v << 1 | 1);
}
ll query(ll i, ll l, ll r, ll v)
{
    if (l == r)
        return st[v];
    ll mid = (l + r) >> 1;
    if (i <= mid)
        return min(st[v], query(i, l, mid, v << 1));
    else
        return min(st[v], query(i, mid + 1, r, v << 1 | 1));
}
vector<pair<ll, ll>> g[N];
ll mn[N], d[N], f[N], timer, p[N], ans[N];
pair<ll, ll> e[N];
vector<pair<ll, ll>> qs[N];
ll n, s, q, root, depth[N];
void init(ll v, ll par = 0)
{
    d[v] = ++timer;
    p[v] = par;
    for (auto [to, w] : g[v])
        if (to != par)
        {
            depth[to] = depth[v] + w;
            init(to, v);
            mn[v] = min(mn[v], mn[to] + w);
        }
    f[v] = timer;
}
void dfs(ll v, ll par = 0)
{
    for (auto [to, w] : g[v])
        if (to != par)
            dfs(to, v);
    modify(d[v], f[v], mn[v] - depth[v], 1, n, 1);
    for (auto [r, ind] : qs[v]) 
        if (!(d[v] <= d[r] and d[r] <= f[v])) ans[ind] = -1;
        else ans[ind] = query(d[r], 1, n, 1) + depth[r];
}
void solve()
{
    cin >> n >> s >> q >> root;
    for (ll i = 1; i <= n; i++)
        mn[i] = 1e18;
    for (ll i = 1; i < n; i++)
    {
        ll a, b, c;
        cin >> a >> b >> c;
        g[a].push_back(make_pair(b, c));
        g[b].push_back(make_pair(a, c));
        e[i] = make_pair(a, b);
    }
    while (s--)
    {
        ll x;
        cin >> x;
        mn[x] = 0;
    }
    init(root);
    for (ll i = 1; i < n; i++)
        if (p[e[i].first] != e[i].second)
            swap(e[i].first, e[i].second);
    build(1, n, 1);
    for (ll i = 0; i < q; i++)
    {
        ll x, y;
        cin >> x >> y;
        qs[e[x].first].push_back(make_pair(y, i));
    }
    dfs(root);
    for (ll i = 0; i < q; i++) if (ans[i] == -1) cout << "escaped\n";
    else if (ans[i] >= 1e18) cout << "oo\n";
    else cout << ans[i] << endl;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    ll t = 1;
    // precomp();
    // cin >> t;
    for (ll cs = 1; cs <= t; cs++)
        solve();
    // cerr << "\nTime elapsed: " << clock() * 1000.0 / CLOCKS_PER_SEC << " ms\n";
}

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