Submission #540279

#	Time	Username	Problem	Language	Result	Execution time	Memory
540279		surgutti	Capital City (JOI20_capital_city)	C++17	100 / 100	1168 ms	49820 KiB

capital_city

#include <bits/stdc++.h>

using namespace std;

const int N = 200'007;

int n, k;
vector<int> adj[N];
int c[N];

vector<int> col[N];
int vis[N], sz[N], par[N], done[N], tim;
vector<int> cur[N];

void prepare(int u, int f) {
    sz[u] = 1;
    cur[c[u]].push_back(u);
    for (int v : adj[u]) if (!vis[v] && v != f) {
        prepare(v, u);
        sz[u] += sz[v];
        par[v] = u;
    }
}

int find_centroid(int u, int f, int all) {
    for (int v : adj[u]) if (!vis[v] && v != f) {
        if (sz[v] >= all / 2) {
            return find_centroid(v, u, all);
        }
    }
    return u;
}

void clear(int u, int f) {
    cur[c[u]].clear();
    for (int v : adj[u]) if (!vis[v] && v != f) {
        clear(v, u);
    }
}

int ans = N;

void solve(int u) {

    prepare(u, u);

    int centroid = find_centroid(u, u, sz[u]);

    clear(u, u);

    prepare(centroid, centroid);

    queue<int> q;
    q.push(c[centroid]);

    ++tim;

    done[c[centroid]] = tim;

    int now = 0;
    while (q.size()) {
        int v = q.front(); q.pop();
        now++;

        if (cur[v].size() != col[v].size()) {
            now = N;
            break;
        }

        for (int w : cur[v]) if (w != centroid) {
            w = par[w];
            if (done[c[w]] != tim) {
                done[c[w]] = tim;
                q.push(c[w]);
            }
        }
    }
   
    ans = min(ans, now - 1);

    clear(centroid, centroid);

    vis[centroid] = true;

    for (int v : adj[centroid]) if (!vis[v]) {
        solve(v);
    }
}

int main() {
    ios::sync_with_stdio(false), cin.tie(nullptr);

    cin >> n >> k;
    for (int i = 0; i < n - 1; i++) {
        int u, v; cin >> u >> v; u--, v--;

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

    for (int i = 0; i < n; i++) {
        cin >> c[i]; c[i]--;
        col[c[i]].push_back(i);
    }

    solve(0);

    cout << ans << '\n';
}

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