Submission #311690

#	Time	Username	Problem	Language	Result	Execution time	Memory
311690		BeanZ	Railway (BOI17_railway)	C++14	100 / 100	279 ms	54796 KiB

railway

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

#define ll long long
#define endl '\n'
const int N = 1e5 + 5;
const int lg = 17;
vector<pair<ll, ll>> node[N];
vector<ll> fuckoff[N];
vector<ll> ans;
ll dep[N], dp[N][18], up[N];
set<ll> st[N];
ll k;
ll LCA(ll u, ll v){
    if (dep[u] > dep[v]) swap(u, v);
    ll dis = dep[v] - dep[u];
    for (int i = lg; i >= 0; i--){
        if (dis & (1 << i)){
            v = dp[v][i];
        }
    }
    if (u == v) return u;
    for (int i = lg; i >= 0; i--){
        if (dp[u][i] != dp[v][i]){
            v = dp[v][i];
            u = dp[u][i];
        }
    }
    return dp[u][0];
}
void dfs2(ll u, ll p){
    for (auto j : node[u]){
        if (j.first == p) continue;
        dfs2(j.first, u);
        if (st[u].size() < st[j.first].size()) swap(st[u], st[j.first]);
        st[u].insert(st[j.first].begin(), st[j.first].end());
    }
    for (auto j : fuckoff[u]) st[u].erase(j);
    if (st[u].size() >= k) ans.push_back(up[u]);
}
void dfs(ll u, ll p){
    for (int i = 1; i <= lg; i++) dp[u][i] = dp[dp[u][i - 1]][i - 1];
    for (auto j : node[u]){
        if (j.first == p) continue;
        dp[j.first][0] = u;
        dep[j.first] = dep[u] + 1;
        up[j.first] = j.second;
        dfs(j.first, u);
    }
}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    if (fopen("A.inp", "r")){
        freopen("test.inp", "r", stdin);
        freopen("test.out", "w", stdout);
    }
    ll n, m;
    cin >> n >> m >> k;
    for (int i = 1; i < n; i++){
        ll u, v;
        cin >> u >> v;
        node[u].push_back({v, i});
        node[v].push_back({u, i});
    }
    dfs(1, 1);
    for (int tc = 1; tc <= m; tc++){
        ll s, lca;
        cin >> s >> lca;
        st[lca].insert(tc);
        for (int i = 1; i < s; i++){
            ll u;
            cin >> u;
            lca = LCA(lca, u);
            st[u].insert(tc);
        }
        fuckoff[lca].push_back(tc);
    }
    dfs2(1, 1);
    sort(ans.begin(), ans.end());
    cout << ans.size() << endl;
    for (auto j : ans) cout << j << " ";
}
/*
*/

Compilation message (stderr)

railway.cpp: In function 'void dfs2(long long int, long long int)':
railway.cpp:40:22: warning: comparison of integer expressions of different signedness: 'std::set<long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
   40 |     if (st[u].size() >= k) ans.push_back(up[u]);
      |         ~~~~~~~~~~~~~^~~~
railway.cpp: In function 'int main()':
railway.cpp:56:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   56 |         freopen("test.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:57:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   57 |         freopen("test.out", "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