Submission #855882

#	Time	Username	Problem	Language	Result	Execution time	Memory
855882		mychecksedad	Mousetrap (CEOI17_mousetrap)	C++17	25 / 100	645 ms	74296 KiB

mousetrap

/* Author : Mychecksdead  */
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define MOD (1000000000+7)
#define MOD1 (998244353)
#define pb push_back
#define all(x) x.begin(), x.end()
#define en cout << '\n'
const int N = 1e6+100, M = 1e5+10, K = 22;

int n, s, t, dp[N], pd[N];
ll ans = 0;
vector<int> g[N];
bool dfs(int v, int p){
  if(v == t) return 1;
  bool ok = 0;
  dp[v] = 0;
  pd[v] = 0;
  vector<int> dps;
  int child_t = -1;
  for(int u: g[v]){
    if(u != p){
      bool b = dfs(u, v);
      if(!b)
        dps.pb(dp[u] + 1);
      if(b)
        child_t = u;
      ok |= b;
    }
  }
  sort(all(dps), greater<int>());
  if(ok){
    pd[v] = pd[child_t] + int(dps.size());
    if(dps.size() == 0)
      dp[v] = dp[child_t];
    else if(dps.size() == 1)
      dp[v] = min(dps[0] + 2 + pd[v] - 1, 1 + dp[child_t]);
    else
      dp[v] = min(max(dps[1] + pd[v] - 1, dp[child_t] + 1), 2 + dps[0] + pd[v] - 1);
  }else{
    dp[v] = dps.size() <= 1 ? int(dps.size()) : dps[1] + (dps.size() - 1);
  }
  // cout << dp[v] << ' ' << v << ' ' << pd[v] << '\n';
  return ok;
}

void solve(){
  cin >> n >> t >> s;
  for(int i = 0; i < n - 1; ++i){
    int u, v; cin >> u >> v;
    g[u].pb(v);
    g[v].pb(u);
  }
  dp[t] = pd[t] = 0;
  dfs(s, 0);
  cout << dp[s];
}


int main(){
  cin.tie(0); ios::sync_with_stdio(0);
  int tt = 1, aa;
  // freopen("in.txt", "r", stdin);
  // freopen("out.txt", "w", stdout);
  while(tt--){
    solve();
  }
  cerr<<"time taken : "<<(float)clock()/CLOCKS_PER_SEC<<" seconds\n";
  return 0;
} 

Compilation message (stderr)

mousetrap.cpp: In function 'int main()':
mousetrap.cpp:63:15: warning: unused variable 'aa' [-Wunused-variable]
   63 |   int tt = 1, aa;
      |               ^~

• Subtask 1: 0 / 20
• Subtask 2: 25 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35