Submission #1104731

#	Time	Username	Problem	Language	Result	Execution time	Memory
1104731		HiepVu217	Valley (BOI19_valley)	C++17	100 / 100	130 ms	35708 KiB

valley

#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 17;
int n, s, q, e, lg;
int ti, in[N], out[N], p[17][N];
long long d[N], f[N], m[17][N], shop[N];
vector <pair <int, int>> adj[N];
pair <int, int> ed[N];
void dfs (int u, int pr)
{
    in[u] = ++ti, f[u] = shop[u];
    for (auto [v, w]: adj[u])
    {
        if (v == pr)
        {
            continue;
        }
        d[v] = d[u] + w;
        dfs (v, u);
        f[u] = min (f[u], f[v] + w);
    }
    out[u] = ti;
}
void dfz (int u, int pr)
{
    p[0][u] = pr, m[0][u] = f[u] - d[u];
    for (int i = 1; i <= lg; ++i)
    {
        p[i][u] = p[i - 1][p[i - 1][u]];
        m[i][u] = min (m[i - 1][u], m[i - 1][p[i - 1][u]]);
    }
    for (auto [v, w]: adj[u])
    {
        if (v == pr)
        {
            continue;
        }
        dfz (v, u);
    }
}
bool check (int u, int v)
{
    return in[u] <= in[v] && in[v] <= out[u];
}
long long calc (int u, int v)
{
    if (u == v)
    {
        return m[0][u];
    }
    long long res = 1e18;
    for (int i = lg; i >= 0; --i)
    {
        if (p[i][u] && check (v, p[i][u]))
        {
            res = min (res, m[i][u]);
            u = p[i][u];
        }
    }
    return min (res, m[0][u]);
}
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> s >> q >> e;
    lg = __lg(n);
    for (int i = 1, u, v, w; i < n; ++i)
    {
        cin >> u >> v >> w;
        adj[u].push_back ({v, w});
        adj[v].push_back ({u, w});
        shop[i] = 1e18, ed[i] = {u, v};
    }
    shop[n] = 1e18;
    for (int i = 1, x; i <= s; ++i)
    {
        cin >> x;
        shop[x] = 0;
    }
    dfs (e, 0);
    dfz (e, 0);
    while (q--)
    {
        int id, x;
        cin >> id >> x;
        auto [u, v] = ed[id];
        int child = (check (u, v) ? v : u);
        if (!check (child, x))
        {
            cout << "escaped\n";
            continue;
        }
        long long ans = calc (x, child) + d[x];
        if (ans > 1e14)
        {
            cout << "oo\n";
            continue;
        }
        cout << ans << "\n";
    }
}

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