Submission #890979

#	Time	Username	Problem	Language	Result	Execution time	Memory
890979		juliany2	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	207 ms	43120 KiB

Main

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(x) (x).begin(), (x).end()

const int N = 2e5 + 7, L = 19;
int n;
int p[N];
vector<int> adj[N];
int lift[N][L], dep[N], e[N];
ll dp[N];

int get(int x) {
    return e[x] == x ? x : e[x] = get(e[x]);
}

void dfs(int v = 1, int p = 0, int d = 0) {
    dep[v] = d;
    lift[v][0] = p;
    for (int i = 1; i < L; i++)
        lift[v][i] = lift[lift[v][i - 1]][i - 1];

    for (int u : adj[v])
        if (u != p)
            dfs(u, v, d + 1);
}

int lca(int u, int v) {
    if (dep[u] > dep[v])
        swap(u, v);

    for (int i = L - 1; ~i; --i)
        if (dep[v] - (1 << i) >= dep[u])
            v = lift[v][i];

    if (u == v)
        return u;

    for (int i = L - 1; ~i; --i)
        if (lift[v][i] != lift[u][i])
            v = lift[v][i], u = lift[u][i];
    return lift[u][0];
}

int dist(int u, int v) {
    return dep[u] + dep[v] - 2 * dep[lca(u, v)];
}

int main() {
    cin.tie(0)->sync_with_stdio(false);

    cin >> n;

    for (int i = 1; i <= n; i++)
        cin >> p[i];

    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;

        u = p[u], v = p[v];
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    dfs();

    iota(e + 1, e + n + 1, 1);

    for (int i = 1; i <= n; i++) {
        for (int u : adj[i]) {
            u = get(u);
            if (u < i) {
                dp[i] = max(dp[i], dp[u] + dist(i, u));
                e[u] = i;
            }
        }
    }

    cout << dp[n] << '\n';

    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26