Submission #619314

#	Time	Username	Problem	Language	Result	Execution time	Memory
619314		Soul234	Railway (BOI17_railway)	C++14	100 / 100	127 ms	24508 KiB

railway

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

void DBG() { cerr << "]\n"; }
template<class H, class... T> void DBG(H h, T... t) {
    cerr << h; if(sizeof...(t)) cerr << ", ";
    DBG(t...);
}
#ifdef LOCAL
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define dbg(...) 0
#endif // LOCAL

#define FOR(i,a,b) for(int i = (a) ; i<(b) ; i++)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for(int i = (b)-1 ; i>=(a) ; i--)
#define R0F(i,a) ROF(i,0,a)
#define each(e,a) for(auto &e : (a))
#define sz(v) (int)(v).size()
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define pb push_back
#define tcT template<class T
#define nl "\n"

using ll = long long;
using vi = vector<int>;
using pi = pair<int,int>;
using str = string;
tcT> using V = vector<T>;
tcT> using pqg = priority_queue<T,vector<T>,greater<T>>;

void setIO(string NAME = "") {
    cin.tie(0)->sync_with_stdio(0);
    if(sz(NAME)) {
        freopen((NAME + ".inp").c_str(),"r",stdin);
        freopen((NAME + ".out").c_str(),"w",stdout);
    }
}

tcT> bool ckmin(T&a, const T&b) {
    return b < a ? a=b,1 : 0; }
tcT> bool ckmax(T&a, const T&b) {
    return b > a ? a=b,1 : 0; }

const int MOD = 1e9 + 7;

struct BIT {
    int N;
    vi bit;
    void init(int _N) {
        N = _N;
        bit.assign(N+7, 0);
    }
    void upd(int p, int val) {
        for(; p<=N; p+=p&-p) bit[p] += val;
    }
    int query(int l, int r) {
        int res = 0;
        for(; r>0; r -= r&-r) res += bit[r];
        for(--l; l>0; l -= l&-l) res -= bit[l];
        return res;
    }
} fen;

const int MX = 1e5+5, LG = 19;
int N, M, K, tin[MX], tout[MX], dep[MX], par[MX][LG], tt, edgeID[MX];
V<pi> adj[MX];

void dfs(int u, int p) {
    tin[u] = ++tt;
    each(ed, adj[u]) if(ed.first != p) {
        int v = ed.first;
        dep[v] = dep[par[v][0] = u] + 1;
        edgeID[v] = ed.second;
        dfs(v, u);
    }
    tout[u] = tt;
}

int get_lca(int a, int b) {
    if(dep[a] < dep[b]) swap(a,b);
    int d = dep[a] - dep[b];
    R0F(i,LG) if(d>>i&1) a = par[a][i];
    if(a == b) return a;
    R0F(i,LG) if(par[a][i] != par[b][i]) {
        a = par[a][i];
        b = par[b][i];
    }
    return par[a][0];
}

bool cmp(const int &a, const int &b) {
    return tin[a] < tin[b];
}

void solve() {
    cin>>N>>M>>K;
    fen.init(N+5);
    F0R(i,N-1) {
        int u,v;
        cin>>u>>v;
        adj[u].pb({v, i+1});
        adj[v].pb({u, i+1});
    }
    par[1][0] = 1;
    dep[1] = 0;
    dfs(1, -1);
    FOR(j,1,LG) FOR(i,1,N+1) par[i][j] = par[par[i][j-1]][j-1];
    F0R(_, M) {
        int amt; cin>>amt;
        vi lst;
        F0R(i, amt) {
            int v; cin>>v;
            lst.pb(v);
        }
        sort(all(lst), cmp);
        F0R(i,sz(lst)) {
            int nxt = (i+1)%sz(lst);
            fen.upd(tin[lst[i]], 1);
            fen.upd(tin[lst[nxt]], 1);
            fen.upd(tin[get_lca(lst[i], lst[nxt])], -2);
        }
    }
    vi ans;
    FOR(i,2,N+1) if(fen.query(tin[i], tout[i]) >= 2*K) {
        ans.pb(edgeID[i]);
    }
    sort(all(ans));
    cout << sz(ans) << nl;
    each(v, ans) cout << v << " ";
    cout << nl;
}

int main() {
    setIO();

    int t=1;
    //cin>>t;
    while(t-->0) {
        solve();
    }

    return 0;
}

Compilation message (stderr)

railway.cpp: In function 'void setIO(std::string)':
railway.cpp:37:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |         freopen((NAME + ".inp").c_str(),"r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:38:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   38 |         freopen((NAME + ".out").c_str(),"w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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