Submission #1127129

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127129		underwaterkillerwhale	Capital City (JOI20_capital_city)	C++20	100 / 100	352 ms	66604 KiB

capital_city

//#include"holiday.h"
#include <bits/stdc++.h>
#define ll long long
#define rep(i,m,n) for(int i=(m); i<=(n); i++)
#define REB(i,m,n) for(int i=(m); i>=(n); i--)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define MP make_pair
#define fs first
#define se second
#define bit(msk, i) ((msk >> i) & 1)
#define iter(id, v) for(auto id : v)
#define pb push_back
#define SZ(v) (ll)v.size()
#define ALL(v) v.begin(),v.end()

using namespace std;

mt19937_64 rd(chrono :: steady_clock :: now ().time_since_epoch().count());
ll Rand (ll l, ll r) { return uniform_int_distribution<ll> (l, r) (rd); }

const int N = 2e5 + 7;
const int Mod = 1e9 + 7;///lon
const ll INF = 1e18 + 7;
const ll BASE = 137;
const int szBL = 450;

int n, K;
int a[N];
vector<int> ke[N], adj[N], vec[N];
int high[N], par[N][25], Anc[N];

int num[N], low[N], del[N], SCC[N], nSCC, sz[N];
int dp[N];

void pdfs (int u, int p) {
    high[u] = high[p] + 1;
    par[u][0] = p;
    rep (i, 1, 20) par[u][i] = par[par[u][i - 1]][i - 1];
    iter (&v, ke[u]) {
        if (v != p) {
            pdfs(v, u);
        }
    }
}

int LCA (int u, int v) {
    if (high[u] > high[v]) swap(u, v);
    rep (i, 0, 20) if (bit(high[v] - high[u], i)) v = par[v][i];
    if (v == u) return v;
    REB (i, 20, 0) if (par[v][i] != par[u][i]) {
        v = par[v][i];
        u = par[u][i];
    }
    return par[v][0];
}

void solution() {
    cin >> n >> K;
    rep (i, 2, n) {
        int u, v;
        cin >> u >> v;
        ke[u].pb(v);
        ke[v].pb(u);
    }
    pdfs(1, 0);
    rep (i, 1, n) {
        int X;
        cin >> X;
        a[i] = X;
        vec[X].pb(i);
    }
    rep (X, 1, K) {
        int anc = 0;
        iter (&u, vec[X]) {
            if (anc == 0) anc = u;
            anc = LCA(anc, u);
        }
        Anc[X] = anc;
    }
    function<void(int, int)> dfs = [&] (int u, int p) {
        if (u != Anc[a[u]]) {
//            cout << a[u] <<" "<<a[p] <<" a\n";
            adj[a[u]].pb(a[p]);
        }
        iter (&v, ke[u]) {
            if (v == p) continue;
            dfs(v, u);
        }
    };
    dfs(1, 0);
    stack<int> st;
    function<void(int)> dfs2 = [&] (int u) {
        static int time_dfs = 0;
        num[u] = low[u] = ++time_dfs;
        st.push(u);
        iter (&v, adj[u]) {
            if (del[v]) continue;
            if (!num[v]) {
                dfs2(v);
                low[u] = min(low[u], low[v]);
            }
            else low[u] = min(low[u], num[v]);
        }
        if (low[u] == num[u]) {
            int v;
            ++nSCC;
            do {
                v = st.top();
                st.pop();
                del[v] = 1;
                SCC[v] = nSCC;
                ++sz[nSCC];
            }while (v != u);

        }
    };
    rep (i, 1, K) {
        if (!num[i]) dfs2(i);
    }
    int res = K;
    rep (u, 1, K) {
        iter (&v, adj[u]) {
            int cu = SCC[u], cv = SCC[v];
            if (cv != cu) dp[cu] = 1;
        }
    }
    rep (u, 1, nSCC) {
        if (dp[u] == 0) {
            res = min(res, sz[u] - 1);
        }
    }

    cout << res <<"\n";
}

#define file(name) freopen(name".inp","r",stdin); \
freopen(name".out","w",stdout);
int main () {
//    file("c");
    ios_base :: sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int num_Test = 1;
//    cin >> num_Test;
    while (num_Test--)
        solution();
}
/*
no bug challenge +36
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*/

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