Submission #623494

#	Time	Username	Problem	Language	Result	Execution time	Memory
623494		welleyth	Capital City (JOI20_capital_city)	C++17	100 / 100	1238 ms	46956 KiB

capital_city

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;

#define int long long
#define mp make_pair
#define pb push_back

#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx2")

constexpr int INF = (int)2e18;
constexpr int N = (int)2e5 + 111;
constexpr int md = (int)998244353;
constexpr int mdPower = (int)1e9+7 - 1;
constexpr double eps = 1e-7;

typedef __int128 _uint;
typedef long long ll;

mt19937_64 rnd(time(nullptr));

void add(int& a,int b){
    a += b; if(a >= md) a -= md;
}
void sub(int& a,int b){
    a -= b; while(a < 0) a += md;
}
void add(__int128& a,int b){
    a += b;
}
void sub(__int128& a,int b){
    a -= b;
}

int bpow(int a,int b){
    if(b == 0)
        return 1;
    if(b % 2 == 0){
        int t = bpow(a,b>>1);
        return 1ll*t*t%md;
    }
    return 1ll * a*bpow(a,b-1) % md;
}

int inv(int a){
    return bpow(a,md-2);
}

int fac[N],invfac[N];

void init(){
    fac[0] = 1;
    for(int i = 1; i < N; i++){
        fac[i] = (fac[i-1] * i) % md;
    }
    invfac[N-1] = inv(fac[N-1]);
    for(int i = N-2; i >= 0; i--){
        invfac[i] = (invfac[i+1] * (i+1))%md;
    }
    return;
}

//int C(int n,int k){
//    if(k > n)
//        return 0;
//    return fac[n] * invfac[k] % md * invfac[n-k] % md;
//}
//
//int A(int n,int k){
//    if(k > n)
//        return 0;
//    return fac[n] * invfac[n-k] % md;
//}

vector<int> g[N];
int col[N];
vector<int> cities[N];
int sz[N];
int ans = INF;
bool used[N];
bool choosen[N];
int p[N];
int L[N];
int d[N];

void dfs1(int v,int pr = -1){
    sz[v] = 1;
    for(auto& to : g[v]){
        if(to == pr || used[to])
            continue;
        dfs1(to,v);
        sz[v] += sz[to];
    }
    return;
}

int getCentroid(int v,int n,int pr = -1){
    for(auto& to : g[v]){
        if(to == pr || used[to])
            continue;
        if(sz[to] > (n+1)/2)
            return getCentroid(to,n,v);
    }
    return v;
}

int CNT = 0;
void dfs3(int v,int pr = -1){
    L[v] = CNT;
    p[v] = pr;
    for(auto& to : g[v]){
        if(to == pr || used[to])
            continue;
        d[to] = d[v] + 1;
        dfs3(to,v);
    }
    return;
}

void solve(int v,int pr = -1){
    dfs1(v);
    int C = getCentroid(v,sz[v]);
//    cerr << "C = " << C << "\n";
    int cur_col = col[C];
    dfs1(C);
    CNT++;
    d[C] = 0;
    dfs3(C);
//    cerr << "ok\n";
    if(!choosen[cur_col]){
        set<int> added_colors;
        added_colors.insert(cur_col);
        set<pair<int,int>> q;
        bool ok = true;
        set<int> visited;
        for(auto& x : cities[cur_col]){
            q.insert(mp(-d[x],x));
            visited.insert(x);
            if(L[x] != CNT){
                ok = false;
                break;
            }
        }
        while(!q.empty() && ok){
            int v = q.begin()->second;
            q.erase(q.begin());
//            cerr << "v = " << v << "\n";
            if(choosen[col[v]]){
                ok = false;
                break;
            }
            if(!added_colors.count(col[v])){
                for(auto& x : cities[col[v]]){
                    if(!visited.count(x)){
                        q.insert(mp(-d[x],x));
                        visited.insert(x);
                    }
                    if(L[x] != CNT){
                        ok = false;
                        break;
                    }
                }
                added_colors.insert(col[v]);
            }
            if(p[v] > 0 && !visited.count(p[v])){
                q.insert(mp(-d[p[v]],p[v]));
                visited.insert(p[v]);
            }
        }
        if(ok){
            ans = min(ans,(int)added_colors.size()-1);
            choosen[cur_col] = 1;
        }
//        cerr << "v = " << v << ", centroid = " << C << "\n";
    }
    used[C] = true;
    for(auto& to : g[C]){
        if(!used[to]){
            solve(to);
        }
    }
    return;
}

void solve(){
    int n,k;
    cin >> n >> k;

    for(int i = 1; i < n; i++){
        int a,b;
        cin >> a >> b;
        g[a].pb(b);
        g[b].pb(a);
    }

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

    solve(1);

    assert(ans != INF);
    cout << ans << "\n";

    return;
}

signed main(){
    ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
    init();
    int tests = 1;
//    cin >> tests;
    for(int test = 1; test <= tests; test++){
//        cerr << "test = " << test << "\n";
        solve();
    }
    return 0;
}
/**

**/

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