Submission #482902

#	Time	Username	Problem	Language	Result	Execution time	Memory
482902		PoPularPlusPlus	Railway (BOI17_railway)	C++17	100 / 100	107 ms	27988 KiB

railway

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long 
#define pb(e) push_back(e)
#define sv(a) sort(a.begin(),a.end())
#define sa(a,n) sort(a,a+n)
#define mp(a,b) make_pair(a,b)
#define vf first
#define vs second
#define ar array
#define all(x) x.begin(),x.end()
const int inf = 0x3f3f3f3f;
const int mod = 1000000007; 
const double PI=3.14159265358979323846264338327950288419716939937510582097494459230;
bool remender(ll a , ll b){return a%b;}

const int N = 100002 , l = 25;
int n , m , k;
vector<pair<int,int>> adj[N];
int cnt[N],timer,tin[N], tout[N],up[N][l + 5];
vector<int> ans;

void dfs(int v, int p){
    tin[v] = ++timer;
    up[v][0] = p;
    for (int i = 1; i <= l; ++i)
        up[v][i] = up[up[v][i-1]][i-1];

    for (auto &[u,ldonewjfjiwjjfosfojg] : adj[v]) {
        if (u != p)
            dfs(u, v);
    }

    tout[v] = ++timer;
}

bool is_ancestor(int u, int v){
    return tin[u] <= tin[v] && tout[u] >= tout[v];
}

int lca(int u, int v){
    if (is_ancestor(u, v))
        return u;
    if (is_ancestor(v, u))
        return v;
    for (int i = l; i >= 0; --i) {
        if (!is_ancestor(up[u][i], v))
            u = up[u][i];
    }
    return up[u][0];
}

bool cmp(int x , int y){
	return tin[x] < tin[y];
}

void dfs1(int node , int par = -1){
	for(auto &[i,idx] : adj[node]){
		if(i!=par){
			dfs1(i,node);
			if(cnt[i] >= 2 * k)ans.pb(idx);
				cnt[node] += cnt[i];
		}
	}
}

void solve(){
	cin >> n >> m >> k;
	for(int i = 1; i < n; i++){
		int u , v;
		cin >> u >> v;
		adj[u].pb(mp(v,i));
		adj[v].pb(mp(u,i));
	}
	timer = 0;
	dfs(1,1);
	memset(cnt,0,sizeof cnt);
	for(int i = 0; i < m; i++){
		int s;
		cin >> s;
		int arr[s];
		for(int j = 0; j < s; j++){
			cin >> arr[j];
		}
		sort(arr,arr+s,cmp);
		for(int j = 0; j < s; j++){
			int lc = lca(arr[j],arr[(j + 1) % s]);
			cnt[lc]-=2;
			cnt[arr[j]]++;
			cnt[arr[(j + 1) % s]]++;
		}
	}
	dfs1(1);
	sv(ans);
	cout << ans.size() << '\n';
	for(int i : ans)cout << i << ' ';
}

int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
	//int t;cin >> t;while(t--)
	solve();
	return 0;
}

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