Submission #597913

#	Time	Username	Problem	Language	Result	Execution time	Memory
597913		Do_you_copy	Railway (BOI17_railway)	C++17	100 / 100	120 ms	24912 KiB

railway

#include <bits/stdc++.h>
#define taskname "test"
#define fi first
#define se second
#define pb push_back
#define faster ios_base::sync_with_stdio(0); cin.tie(0);
using namespace std;
using ll = long long;
using pii = pair <int, int>;
using pil = pair <int, ll>;
using pli = pair <ll, int>;
using pll = pair <ll, ll>;
using ull = unsigned ll;
mt19937 Rand(chrono::steady_clock::now().time_since_epoch().count());

ll min(const ll &a, const ll &b){
    return (a < b) ? a : b;
}

ll max(const ll &a, const ll &b){
    return (a > b) ? a : b;
}

//const ll Mod = 1000000007;
//const ll Mod2 = 999999999989;
//only use when required
const int maxN = 1e5 + 1;

int n, m, k;
int num[maxN];
int depth[maxN];
int timedfs;
int bit[maxN];
int lift[maxN][20];
int child[maxN];
int val[maxN];
vector <pii> adj[maxN];
void pre_dfs(int u, int p){
    depth[u] = depth[p] + 1;
    lift[u][0] = p;
    num[u] = ++timedfs;
    for (int i = 1; i < 20; ++i){
        lift[u][i] = lift[lift[u][i - 1]][i - 1];
    }
    for (const auto &i: adj[u]){
        if (i.fi == p) continue;
        pre_dfs(i.fi, u);
        child[u] += child[i.fi] + 1;
    }
}

vector <int> answ;
void dfs(int u, int p){
    for (const auto &i: adj[u]){
        if (i.fi == p) continue;
        dfs(i.fi, u);
        val[u] += val[i.fi];
        if (val[i.fi] >= k){
            answ.pb(i.se);
        }
    }
}

int lca(int u, int v){
    if (depth[u] < depth[v]) swap(u, v);
    int k = (depth[u] - depth[v]);
    while (k){
        int t = k & -k;
        u = lift[u][__lg(t)];
        k ^= t;
    }
    if (u == v) return u;
    for (int i = 19; i >= 0; --i){
        if (lift[u][i] != lift[v][i]){
            u = lift[u][i];
            v = lift[v][i];
        }
    }
    return lift[u][0];
}

void update(int x, int val){
    for (; x <= n; x += x & -x){
        bit[x] += val;
    }
}

int get(int x){
    int ans = 0;
    for (; x; x -= x & -x) ans += bit[x];
    return ans;
}

void Init(){
    cin >> n >> m >> k;
    for (int i = 1; i < n; ++i){
        int u, v;
        cin >> u >> v;
        adj[u].pb({v, i});
        adj[v].pb({u, i});
    }
    pre_dfs(1, 0);
    for (int i = 1; i <= m; ++i){
        int S; cin >> S;
        vector <int> v(S);
        for (int &j: v) cin >> j;
        sort(v.begin(), v.end(),[](const int &i, const int &j){
            return depth[i] > depth[j];
        });
        int last = v[0];
        ++val[v[0]];
        update(num[v[0]], 1);
        for (int j = 1; j < S; ++j){
            int u = v[j];
            last = lca(last, u);
            int t = get(num[u] + child[u]) - get(num[u]);
            if (t){
            update(num[v[j]], 1);
                continue;
            }
            ++val[u];
            for (int i = 19; i >= 0; --i){
                int anc = lift[u][i];
                if (anc == 0) continue;
                if (!(get(num[anc] + child[anc]) - get(num[anc]))){
                    u = anc;
                }
            }
            u = lift[u][0];
            --val[u];
            update(num[v[j]], 1);
        }
        --val[last];
        for (int j: v){
            update(num[j], -1);
        }
    }
    dfs(1, 0);
    cout << answ.size() << "\n";
    sort(answ.begin(), answ.end());
    for (int i: answ) cout << i << " ";
}


int main(){
    if (fopen(taskname".inp", "r")){
        freopen(taskname".inp", "r", stdin);
        //freopen(taskname".out", "w", stdout);
    }
    faster;
    ll tt = 1;
    //cin >> tt;
    while (tt--){
        Init();
    }
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:147:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  147 |         freopen(taskname".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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