Submission #1190549

#	Time	Username	Problem	Language	Result	Execution time	Memory
1190549		KaleemRazaSyed	Wells (CEOI21_wells)	C++20	0 / 100	46 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 mark[N];

bool Close;

void Dfs(int v, int p = -1, int d = 1)
{
  if(Close || d > k) return;

  if(d <= k && d != 1)
    Close |= mark[v]; 

  for(int u : G[v])
    if(u != p)
      Dfs(u, v, d + 1); 
}

void dFs(int v, int p = -1, int d = 1)
{
  if(Close || d > k) return;

  if(d == k)
    Close = true;
  
  for(int u : G[v])
    {
      if(u == p) continue;
      if(!mark[u])
	dFs(u, v, d + 1);
    }
}

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

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

  vector<int> vec;
  
  Close = false;  

  while(level.size())
    {
      // cerr << l << endl;
      if(l == 1)
	for(int x : level)
	  vec.push_back(x);
      
      vector<int> nl;
      for(int x : level)
	  for(int u : G[x])
	    if(!seen[u])
	      seen[u] = 1, nl.push_back(u);

      l = l % k + 1;
      level = nl;
    }
  // cerr << "k = " << k << endl;
  // cerr << "vec = ";
  for(int u : vec)
    {
      // cerr  << u << ' ';
      mark[u] = true;
    }
  // cerr << endl;
  
  for(int i = 1; i <= n; i ++)
    if(mark[i])
      Dfs(i);
    else
      dFs(i);

  for(int v : vec)
    mark[v] = false;
  
  return !Close;
}

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 ans = 0;
  for(int v = 1; v <= n; 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