Submission #964636

#	Time	Username	Problem	Language	Result	Execution time	Memory
964636		Alihan_8	Railway (BOI17_railway)	C++17	100 / 100	275 ms	41208 KiB

railway

#include <bits/stdc++.h>

using namespace std;

#define all(x) x.begin(), x.end()
#define ar array
#define pb push_back
#define ln '\n'
#define int long long

using i64 = long long;

template <class F, class _S>
bool chmin(F &u, const _S &v){
    bool flag = false;
    if ( u > v ){
        u = v; flag |= true;
    }
    return flag;
}

template <class F, class _S>
bool chmax(F &u, const _S &v){
    bool flag = false;
    if ( u < v ){
        u = v; flag |= true;
    }
    return flag;
}

const int inf = 1e15;

const int N = 1e5 + 1;

int n;

struct SegTree{
    vector <int> T;

    SegTree(){
        T.resize(N * 4, inf);
    }

    void upd(int v, int l, int r, int p, int val){
        if ( l == r ){
            T[v] = val;
            return;
        }
        int md = (l + r) >> 1;
        if ( p <= md ){
            upd(v * 2, l, md, p, val);
        } else{
            upd(v * 2 + 1, md + 1, r, p, val);
        }
        T[v] = min(T[v * 2], T[v * 2 + 1]);
    }

    void upd(int p, int val){
        upd(1, 0, n - 1, p, val);
    }

    int get(int v, int l, int r, int tl, int tr){
        if ( l > tr or r < tl ){
            return inf;
        }
        if ( tl <= l && tr >= r ){
            return T[v];
        }
        int md = (l + r) >> 1;
        return min(get(v * 2, l, md, tl, tr), get(v * 2 + 1, md + 1, r, tl, tr));
    }

    int get(int l, int r){
        return get(1, 0, n - 1, l, r);
    }
} seg;

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int m, k; cin >> n >> m >> k;
    vector <vector<ar<int,2>>> G(n);
    for ( int i = 0; i + 1 < n; i++ ){
        int u, v; cin >> u >> v;
        --u, --v;
        G[u].pb({v, i});
        G[v].pb({u, i});
    }
    vector <int> d(n), tin(n), tout(n), rev(n);
    vector <vector<int>> up(20, vector <int> (n));
    int ct = -1;
    auto dfs = [&](auto dfs, int u, int p) -> void{
        up[0][u] = p;
        for ( int i = 1; i < 20; i++ ){
            up[i][u] = up[i - 1][up[i - 1][u]];
        }
        tin[u] = ++ct;
        rev[tin[u]] = u;
        for ( auto &[v, j]: G[u] ){
            if ( v != p ){
                d[v] = d[u] + 1;
                dfs(dfs, v, u);
            }
        } tout[u] = ct;
    };
    dfs(dfs, 0, 0);
    auto lca = [&](int u, int v){
        if ( d[u] < d[v] ) swap(u, v);
        int df = d[u] - d[v];
        for ( int i = 0; i < 20; i++ ){
            if ( df >> i & 1 ){
                u = up[i][u];
            }
        }
        if ( u == v ){
            return u;
        }
        for ( int i = 19; i >= 0; i-- ){
            if ( up[i][u] != up[i][v] ){
                u = up[i][u];
                v = up[i][v];
            }
        }
        return up[0][u];
    };
    vector <int> cnt(n);
    auto rec = [&](auto rec, int u) -> void{
        seg.upd(tin[u], inf);
        while ( true ){
            int x = seg.get(tin[u], tout[u]);
            if ( x == inf ) break;
            x = rev[x];
            cnt[u]--, cnt[x]++;
            rec(rec, x);
        }
    };
    for ( int i = 0; i < m; i++ ){
        int s; cin >> s;
        vector <int> a(s);
        int p = -1;
        for ( auto &u: a ){
            cin >> u; --u;
            if ( p == -1 ){
                p = u;
            } else p = lca(u, p);
            seg.upd(tin[u], tin[u]);
        }
        sort(all(a), [&](int &u, int &v){
             return tin[u] < tin[v];
        });
        for ( int j = 1; j < s; j++ ){
            int p = lca(a[j - 1], a[j]);
            seg.upd(tin[p], tin[p]);
        }
        rec(rec, p);
    }
    vector <int> ans;
    auto dfs2 = [&](auto dfs2, int u, int p) -> void{
        for ( auto &[v, j]: G[u] ){
            if ( v != p ){
                dfs2(dfs2, v, u);
                if ( cnt[v] >= k ){
                    ans.pb(j);
                }
                cnt[u] += cnt[v];
            }
        }
    };
    dfs2(dfs2, 0, 0);
    sort(all(ans));
    cout << ans.size() << ln;
    for ( auto &u: ans ){
        cout << u + 1 << ' ';
    }

    cout << '\n';
}

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