Submission #319166

#	Time	Username	Problem	Language	Result	Execution time	Memory
319166		VodkaInTheJar	Untitled (POI11_dyn)	C++14	40 / 100	33 ms	4332 KiB

Main

#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#define endl '\n'

using namespace std;

const int maxn = 1003; 

int n, m; 
vector <int> v; 
vector <int> adj[maxn];
void read()
{
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
	{
		bool is;
		cin >> is;
		
		if (is)
		v.push_back(i);
	}
	
	for (int i = 1; i <= n-1; i++)
	{
		int a, b;
		cin >> a >> b;
		
		adj[a].push_back(b);
		adj[b].push_back(a);
	}
}

int dist[maxn][maxn];
void dfs(int start, int ver, int par)
{
	for (auto i: adj[ver])
	if (i != par)
	{
		dist[start][i] = dist[start][ver] + 1;
		dfs(start, i, ver);
	}
}

int depth[maxn], pr[maxn];
void dfs1(int ver, int par)
{
	for (auto i: adj[ver])
	if (i != par)
	{
		pr[i] = ver;
		depth[i] = depth[ver] + 1; 
		dfs1(i, ver);
	}
}

bool is_covered[maxn];
bool can(int x)
{
	vector <pair <int, int> > v1; 
	for (auto i: v)
	v1.push_back({depth[i], i});
	
	sort(v1.begin(), v1.end());
	reverse(v1.begin(), v1.end());
	
	for (int i = 1; i <= n; i++)
	is_covered[i] = false;
	
	int cnt = 0;
	for (auto i: v1)
	{
		if (is_covered[i.second])
		continue;
		
		cnt++;
		int curr = i.second;
		for (int i = 1; i <= x && curr != 1; i++)
		curr = pr[curr];
		
		for (auto j: v)
		if (dist[j][curr] <= x)
		is_covered[j] = true; 
	}
	
	return cnt <= m; 
}

void solve()
{
	for (int i = 1; i <= n; i++)
	{
		dist[i][i] = 0;
		dfs(i, i, -1);
	}
	
	depth[1] = 1; 
	pr[1] = -1;
	dfs1(1, -1);
	
	int low = 0, high = n; 
	while (low < high)
	{
		int mid = (low + high) / 2;
		if (can(mid))
		high = mid;
		
		else 
		low = mid+1;
	}
	
	cout << low << endl;
}

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

	read();
	solve();
}

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10