Submission #884748

#	Time	Username	Problem	Language	Result	Execution time	Memory
884748		Shayan86	Railway (BOI17_railway)	C++14	100 / 100	108 ms	33108 KiB

railway

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

#pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// Ofast, O0, O1, O2, O3, unroll-loops, fast-math, trapv

typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;

#define Mp          make_pair
#define sep         ' '
#define endl        '\n'
#define F	        first
#define S	        second
#define pb          push_back
#define all(x)      (x).begin(),(x).end()
#define kill(res)	cout << res << '\n', exit(0);
#define set_dec(x)	cout << fixed << setprecision(x);
#define fast_io     ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io     freopen("input.txt", "r", stdin) ; freopen("output.txt", "w", stdout);

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const ll L = 20;
const ll N = 1e5 + 50;
const ll Mod = 1e9 + 7;

ll n, m, k, st[N], timer, h[N], par[N][L], id[N], cnt[N];

vector<pii> adj[N];

void dfs(int v, int p = 0){
    par[v][0] = p;
    for(int i = 1; i < L; i++){
        if(!par[v][i-1]) break;
        par[v][i] = par[par[v][i-1]][i-1];
    }

    st[v] = ++timer;
    for(auto [u, i]: adj[v]){
        if(u == p) continue;
        h[u] = h[v] + 1; id[i] = u;
        dfs(u, v);
    }
}

int getPar(int v, int x){
    for(int i = 0; i < L; i++){
        if(x >> i & 1) v = par[v][i];
    }
    return v;
}

int lca(int v, int u){
    if(h[v] < h[u]) swap(u, v);
    v = getPar(v, h[v] - h[u]);
    if(u == v) return v;

    for(int i = L-1; i >= 0; i--){
        if(par[v][i] != par[u][i]){
            v = par[v][i]; u = par[u][i];
        }
    }
    return par[v][0];
}

void cal(int v){
    for(auto [u, i]: adj[v]){
        if(u == par[v][0]) continue;
        cal(u); cnt[v] += cnt[u];
    }
}

int main(){
    fast_io;

    cin >> n >> m >> k;

    int u, v;
    for(int i = 1; i < n; i++){
        cin >> u >> v;
        adj[u].pb(Mp(v, i));
        adj[v].pb(Mp(u, i));
    }

    dfs(1);

    while(m--){
        int si; cin >> si;

        set<pii> ver;
        for(int i = 1; i <= si; i++){
            cin >> v; ver.insert({st[v], v});
        }

        while(ver.size() > 1){
            auto lst1 = *ver.rbegin(); ver.erase(lst1);
            auto lst2 = *ver.rbegin();
            int l = lca(lst1.S, lst2.S);

            cnt[lst1.S]++; cnt[l]--;
            ver.insert({st[l], l});
        }
    }
    //for(int i = 1; i <= n; i++) cout << cnt[i] << sep;

    cal(1);

    int res = 0;
    for(int i = 1; i < n; i++) if(cnt[id[i]] >= k) res++;
    
    cout << res << endl;
    for(int i = 1; i < n; i++) if(cnt[id[i]] >= k) cout << i << sep;

}

Compilation message (stderr)

railway.cpp: In function 'void dfs(int, int)':
railway.cpp:42:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   42 |     for(auto [u, i]: adj[v]){
      |              ^
railway.cpp: In function 'void cal(int)':
railway.cpp:70:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   70 |     for(auto [u, i]: adj[v]){
      |              ^

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 16 / 16
• Subtask 6: 25 / 25