Submission #714028

#	Time	Username	Problem	Language	Result	Execution time	Memory
714028		nifeshe	Pastiri (COI20_pastiri)	C++17	0 / 100	1076 ms	524288 KiB

pastiri

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

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

#define f first
#define s second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((int) (x).size())
#define pb push_back
#define mp make_pair
//#define int long long

using namespace std;
using namespace __gnu_pbds;

template <typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T> inline bool umin(T &a, const T &b) { if(a > b) { a = b; return 1; } return 0; }
template <typename T> inline bool umax(T &a, const T &b) { if(a < b) { a = b; return 1; } return 0; }

typedef long long ll;
typedef long double ld;

const ll mod = 1e9 + 7;
const ll base = 1e6 + 9;
const ll inf = 1e9;
const int MAX = 5e5 + 15;
const int LG = 19;

random_device rd;
mt19937 gen(rd());
uniform_int_distribution<ll> dis(1, inf);

int n;
int timer = 0;
int tin[MAX], tout[MAX], d[MAX];
int up[MAX][LG];
vector<int> g[MAX];

void dfs(int v, int p = 0) {
    tin[v] = timer++;
    up[v][0] = p;
    for(auto to : g[v]) {
        if(to == p) continue;
        d[to] = d[v] + 1;
        dfs(to, v);
    }
    tout[v] = timer;
}

bool anc(int u, int v) {
    return (tin[u] <= tin[v] && tout[u] >= tout[v]);
}

int LCA(int u, int v) {
    if(anc(u, v)) return u;
    if(anc(v, u)) return v;
    for(int l = LG - 1; ~l; l--) {
        if(!anc(up[u][l], v)) u = up[u][l];
    }
    return up[u][0];
}

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

vector<int> bfs(int s) {
    vector<int> d(n + 1, inf);
    queue<int> q;
    q.push(s);
    d[s] = 0;
    while(sz(q)) {
        int v = q.front(); q.pop();
        for(auto to : g[v]) {
            if(d[to] > d[v] + 1) {
                d[to] = d[v] + 1;
                q.push(to);
            }
        }
    }
    return d;
}

void solve() {
    int k;
    cin >> n >> k;
    for(int i = 0; i < n - 1; i++) {
        int u, v;
        cin >> u >> v;
        g[u].pb(v);
        g[v].pb(u);
    }
    vector<int> a(k);
    for(auto &i : a) {
        cin >> i;
    }
    dfs(1);
    vector<vector<int>> d(n + 1, vector<int>(k));
    for(int i = 0; i < k; i++) {
        auto dist = bfs(a[i]);
        for(int v = 1; v <= n; v++) {
            d[v][i] = dist[v];
        }
    }
    vector<int> ans;
    vector<int> used(k);
    int left = k;
    while(left) {
        pair<int, int> best = {0, 0};
        for(int v = 1; v <= n; v++) {
            int cnt = 0;
            int mn = inf;
            for(int i = 0; i < k; i++) {
                if(mn > d[v][i]) {
                    cnt = used[i] ^ 1;
                    mn = d[v][i];
                }
                else if(mn == d[v][i]) {
                    cnt += used[i] ^ 1;
                }
            }
            umax(best, {cnt, v});
        }
        auto [cnt, v] = best;
        left -= cnt;
        int mn = *min_element(all(d[v]));
        for(int i = 0; i < k; i++) {
            if(d[v][i] == mn) used[i] = 1;
        }
        ans.pb(v);
    }
    sort(all(ans));
    cout << sz(ans) << '\n';
    for(auto v : ans) cout << v << " ";
}

signed main() {
    tout[0] = inf;
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    int ttt = 1;
//    cin >> ttt;
    while(ttt--) solve();
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 18
• Subtask 3: 0 / 23
• Subtask 4: 0 / 51