Submission #210675

#	Time	Username	Problem	Language	Result	Execution time	Memory
210675		super_j6	Railway (BOI17_railway)	C++14	36 / 100	456 ms	31604 KiB

railway

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
#define endl '\n'
#define pi pair<int, int>
#define f first
#define s second

struct segTree{
	int l, r;
	segTree *left, *right;
	int val = 0;
	
	segTree(int a, int b){
		l = a;
		r = b;
		
		if(l != r){
			int mid = (l + r) / 2;
			left = new segTree(l, mid);
			right = new segTree(mid + 1, r);
		}
	}
	
	void add(int x, int v){
		if(x < l || r < x) return;
		if(l == r){
			val += v;
			return;
		}
		
		left->add(x, v);
		right->add(x, v);
		val = left->val + right->val;
	}
	
	int qry(int a, int b){
		if(b < l || r < a) return 0;
		if(a <= l && r <= b) return val;
		
		return left->qry(a, b) + right->qry(a, b);
	}
};

const int maxn = 100000, w = 18;
int n, m, k;
int a[maxn], b[maxn], l[maxn], r[maxn], d[maxn], dp[maxn];
int p[w][maxn];
vector<pi> graph[maxn];
segTree tre(0, maxn);
vector<int> ans;

int dfs(int c){
	r[c] = l[c];
	for(pi i : graph[c]){
		if(i.f == p[0][c]) continue;
		d[i.f] = d[c] + 1;
		l[i.f] = r[c] + 1;
		p[0][i.f] = c;
		r[c] = dfs(i.f);
	}
	return r[c];
}

int lca(int x, int y){
	if(d[x] < d[y]) swap(x, y);
	for(int i = w - 1; i >= 0; i--) if(p[i][x] != -1 && d[p[i][x]] >= d[y]) x = p[i][x];
	for(int i = w - 1; i >= 0; i--){
		if(p[i][x] != p[i][y]){
			x = p[i][x];
			y = p[i][y];
		}
	}
	return x == y ? x : p[0][x];
}

void dfs2(int c){
	for(pi i : graph[c]){
		if(i.f == p[0][c]) continue;
		dfs2(i.f);
		if(dp[i.f] >= k) ans.push_back(i.s);
		dp[c] += dp[i.f];
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	
	cin >> n >> m >> k;

	for(int i = 0; i < n - 1; i++){
		int u, v;
		cin >> u >> v;
		u--, v--;
		graph[u].push_back({v, i + 1});
		graph[v].push_back({u, i + 1});
	}
	
	p[0][0] = -1;
	dfs(0);
	
	for(int i = 1; i < w; i++)
	for(int j = 0; j < n; j++){
		p[i][j] = p[i - 1][j] == -1 ? -1 : p[i - 1][p[i - 1][j]];
	}
	
	for(int i = 0; i < m; i++){
		int s;
		cin >> s;
		
		for(int j = 0; j < s; j++){
			cin >> a[j];
			a[j]--;
		}
		sort(a, a + s, [&](int x, int y){
			return d[x] > d[y];	
		});
		
		int lc = a[0];
		for(int j = 0; j < s; j++){
			lc = lca(lc, a[j]);
			b[j] = -tre.qry(l[a[j]], r[a[j]]) + 1;
			dp[a[j]] += b[j];
			tre.add(l[a[j]], b[j]);
		}
		dp[lc] -= tre.qry(l[lc], r[lc]);
		for(int j = 0; j < s; j++){
			tre.add(l[a[j]], -b[j]);
		}
	}
	
	dfs2(0);
	sort(ans.begin(), ans.end());
	
	cout << ans.size() << endl;
	if(!ans.empty()) cout << ans[0];
	for(int i = 1; i < ans.size(); i++) cout << " " << ans[i];
	cout << endl;

	return 0;
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:140:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 1; i < ans.size(); i++) cout << " " << ans[i];
                 ~~^~~~~~~~~~~~

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 0 / 16
• Subtask 6: 0 / 25