Submission #877194

#	Time	Username	Problem	Language	Result	Execution time	Memory
877194		kh0i	Pastiri (COI20_pastiri)	C++17	100 / 100	485 ms	82168 KiB

pastiri

#include "bits/stdc++.h"
using namespace std;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...)
#endif

using ll = long long;
using pii = pair<int, int>;

#define F first
#define S second
#define sz(x) (int)((x).size())
#define all(x) (x).begin(), (x).end()

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll get_rand(ll l, ll r) {
    assert(l <= r);
    return uniform_int_distribution<ll> (l, r)(rng);
}

const int N = 5e5 + 3;

int n, k, x[N];
vector<int> g[N];
int dist[N], h[N], opt[N];

void bfs(){
    memset(dist, 0x3f, sizeof(dist));
    queue<int> qu;
    for(int i = 1; i <= k; ++i){
        dist[x[i]] = 0;
        qu.push(x[i]);
    }

    while(!qu.empty()){
        int u = qu.front();
        qu.pop();
        for(int v : g[u]){
            if(dist[v] > dist[u] + 1){
                dist[v] = dist[u] + 1;
                qu.push(v);
            }
        }
    }
}

void dfs_pre(int u, int pre, int mx, int st){
    int p = h[u] + dist[u];
    if(p > mx){
        mx = p;
        st = u;
    }
    opt[u] = st;
    for(int v : g[u]){
        if(v == pre)
            continue;
        h[v] = h[u] + 1;
        dfs_pre(v, u, mx, st);
    }
}

bool good[N];

void dfs_fill(int u){
    good[u] = 1;
    for(int v : g[u])
        if(!good[v] and dist[v] + 1 == dist[u])
            dfs_fill(v);
}

void solve(){
    cin >> n >> k;
    for(int i = 1; i < n; ++i){
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    for(int i = 1; i <= k; ++i)
        cin >> x[i];
    bfs();
    dfs_pre(1, 0, -1, 1);
    sort(x + 1, x + k + 1, [](int &dak, int &mim) -> bool{
         return h[dak] > h[mim];
         });
    vector<int> res;
    for(int i = 1; i <= k; ++i){
        if(!good[x[i]]){
            res.push_back(opt[x[i]]);
            dfs_fill(opt[x[i]]);
        }
    }
    cout << sz(res) << '\n';
    for(int i : res)
        cout << i << ' ';
}

int32_t main() {
    cin.tie(nullptr)->sync_with_stdio(0);
    #define task "sheep"
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    int test = 1;
//    cin >> test;
    for(int i = 1; i <= test; ++i){
//        cout << "Case #" << i << ": ";
        solve();
    }
    #ifdef LOCAL
        cerr << "\n[Time]: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
    #endif
    return 0;
}

Compilation message (stderr)

pastiri.cpp: In function 'int32_t main()':
pastiri.cpp:105:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  105 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
pastiri.cpp:106:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  106 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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