Submission #1190505

#	Time	Username	Problem	Language	Result	Execution time	Memory
1190505		KaleemRazaSyed	Wells (CEOI21_wells)	C++20	0 / 100	18 ms	35656 KiB

wells

#include<bits/stdc++.h>

using namespace std;

const int N = 1.5e6 + 10, mod = 1e9+7;
int n, k;
vector<int> G[N];
bool done[N];

int dfs(int v, int p = -1)
{
  int ans = 0;
  for(int u : G[v])
    if(u != p)
      ans = max(ans, 1 + dfs(u, v));
  return ans;
}

int diameter()
{
  int ans = 0;
  for(int v = 1; v <= n; v ++)
    ans = max(ans, dfs(v));
  return ans;
}

bool check(int v)
{
  bool seen[n + 1] = {};

  seen[v] = 1;
  
  vector<int> level = {v};
  int l = 0;

  vector<int> vec;
  
  while(level.size())
    {
      if(l % k == 0)
	for(int v : level)
	  vec.push_back(v);
      
      vector<int> nl;
      for(int v : level)
	{
	  int cnt = 0;
	  for(int u : G[v])
	    if(!seen[u])
	      cnt++, seen[u] = 1, nl.push_back(u);

	  if(cnt > 1 && l % k == k-1)
	    return false; 
	}
      l++;
      level = nl;
    }
  
  for(int v : vec) done[v] = 1;
  return true;
}

int main()
{
  cin >> n >> k;

  if(k == 2)
    {
      cout << "YES\n";
      cout << 2 << endl;
      return 0;
    }
  
  for(int i = 1; i < n; i ++)
    {
      int a, b;
      cin >> a >> b;
      G[a].push_back(b);
      G[b].push_back(a);
    }

  int x = diameter();

  if(x < k)
    {
      cout << "YES\n";
      int ans = 1;
      for(int i = 0; i < n; i ++)
	ans = (ans * 2) % mod;
      cout << ans << endl;
      return 0;
    }

  int ans = 0;
  for(int v = 1; v <= n; v++)
    if(!done[v])
      ans += check(v);
  
  cout << (ans == 0 ? "NO" : "YES") << endl;
  cout << ans << endl;
  
  return 0;
}

• Subtask 1: 0 / 30
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 30