Submission #898664

#	Time	Username	Problem	Language	Result	Execution time	Memory
898664		juliany2	Capital City (JOI20_capital_city)	C++17	11 / 100	53 ms	9044 KiB

capital_city

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

const int N = 2007, L = 13;
int n, k;
vector<int> adj[N], col[N], g[N], rev[N], topo, comp;
int c[N], lift[N][L], dep[N], head[N];
bool vis[N];

void dfs(int v = 1, int p = 0) {
    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) {
            dep[u] = dep[v] + 1;
            dfs(u, v);
        }
    }
}

void dfs1(int v) {
    vis[v] = 1;
    for (int u : g[v])
        if (!vis[u])
            dfs1(u);
    topo.push_back(v);
}

void dfs2(int v) {
    vis[v] = 1;
    comp.push_back(v);
    for (int u : rev[v])
        if (!vis[u])
            dfs2(u);
}

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

    cin >> n >> k;

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

        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    for (int i = 1; i <= n; i++) {
        cin >> c[i];
        col[c[i]].push_back(i);
    }

    dfs();

    for (int i = 1; i <= k; i++) {
        int l = col[i][0];
        for (int v : col[i])
            l = lca(l, v);

        g[i].push_back(c[l]);
        for (int v : col[i]) {
            while (v != l) {
                g[i].push_back(c[v]);
                v = lift[v][0];
            }
        }

        sort(all(g[i]));
        g[i].erase(unique(all(g[i])), g[i].end());

        for (int u : g[i])
            rev[u].push_back(i);
    }

    for (int i = 1; i <= k; i++)
        if (!vis[i])
            dfs1(i);

    reverse(all(topo));
    memset(vis, 0, sizeof(vis));

    int ans = k - 1;
    for (int v : topo) {
        if (!vis[v]) {
            comp.clear();
            dfs2(v);

            for (int x : comp)
                head[x] = comp.front();

            bool out = 0;
            for (int x : comp) {
                for (int u : g[x]) {
                    if (head[u] != head[x])
                        out = 1;
                }
            }

            if (!out)
                ans = min(ans, (int) comp.size() - 1);
        }
    }

    cout << ans << '\n';

    return 0;
}

• Subtask 1: 1 / 1
• Subtask 2: 10 / 10
• Subtask 3: 0 / 30
• Subtask 4: 0 / 59