Submission #319189

#	Time	Username	Problem	Language	Result	Execution time	Memory
319189		VodkaInTheJar	Untitled (POI11_dyn)	C++14	0 / 100	521 ms	31460 KiB

Main

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

using namespace std;

const int maxn = 3e5 + 3; 

int n, m; 
bool is[maxn];
vector <pair <int, int> > adj[maxn];
void read()
{
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
	cin >> is[i];
	
	for (int i = 1; i <= n-1; i++)
	{
		int a, b;
		cin >> a >> b;
		
		adj[a].push_back({0, b});
		adj[b].push_back({0, a});
	}
}

int depth[maxn], max_depth[maxn];
void pre_dfs(int ver, int par)
{
	max_depth[ver] = -1;
	if (is[ver])
	max_depth[ver] = depth[ver];
	
	for (auto i: adj[ver])
	if (i.second != par)
	{
		depth[i.second] = depth[ver] + 1; 
		pre_dfs(i.second, ver);
		max_depth[ver] = max(max_depth[ver], max_depth[i.second]);
	}
}

int cnt; 
pair <int, int> dfs(int ver, int par, int cover, int x)
{
	if (max_depth[ver] - depth[ver] <= cover)
	return {0, 0};
	
	if (max_depth[ver] - depth[ver] <= x)
	{
		cnt++;
		return {x, 0}; 
	}
	
	int curr_cover = cover, curr_max_depth = 0;
	for (auto i: adj[ver])
	if (i.second != par)
	{
		auto curr = dfs(i.second, ver, max(0, curr_cover - 1), x);
		curr_cover = max(curr_cover, curr.first);
		curr_max_depth = max(curr_max_depth, curr.second);
	}
    
    if (is[ver])
    curr_max_depth = max(curr_max_depth, depth[ver]);
    
    if (curr_max_depth - depth[ver] < curr_cover)
    curr_max_depth = 0;
    
    else
    if (curr_max_depth == 1)
    {
		cnt++;
		return {0, 0};
	}
	
	else 
	if (curr_max_depth - depth[ver] == x)
	{
		cnt++;
		return {x, 0};
	}
	
	else 
	return {curr_cover - 1, curr_max_depth};
}

bool can(int x)
{
	cnt = 0;
	dfs(1, -1, 0, x);
    
    return cnt <= m; 	
}

void solve()
{
	depth[1] = 1;
	pre_dfs(1, -1);
	
	for (int i = 1; i <= n; i++)
	{
		for (auto &j: adj[i])
		j.first = max_depth[j.second];
		
		sort (adj[i].begin(), adj[i].end());
		reverse(adj[i].begin(), adj[i].end());
	}
	
	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();
}

Compilation message (stderr)

dyn.cpp: In function 'std::pair<int, int> dfs(int, int, int, int)':
dyn.cpp:69:20: warning: control reaches end of non-void function [-Wreturn-type]
   69 |     curr_max_depth = 0;
      |     ~~~~~~~~~~~~~~~^~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 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