Submission #1227943

#	Time	Username	Problem	Language	Result	Execution time	Memory
1227943		thewizardman	Torrent (COI16_torrent)	C++20	69 / 100	553 ms	24764 KiB

torrent

#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include <bits/stdc++.h>
using namespace std;

// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
// template<typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define ll long long
#define ull unsigned long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pli pair<ll, int>
#define plpll pair<ll, pll>
#define pipii pair<int, pii>
#define plpii pair<ll, pii>
#define pipll pair<int, pll>
#define lll tuple<ll, ll, ll>
#define iii tuple<int, int, int>
#define lii tuple<ll, int, int>
#define lli tuple<ll, ll, int>
#define md 1000000007LL
#define linf 0x3f3f3f3f3f3f3f3f
#define inf 0x3f3f3f3f
#define lninf (ll)0xc0c0c0c0c0c0c0c0
#define ninf (int)0xc0c0c0c0
#define bruh ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define ss << ' ' <<
#ifdef wizard
  #define usaco(x)
#else
  #define usaco(x) ifstream cin(#x ".in"); ofstream cout(#x ".out");
#endif

template<class T1, class T2>
istream& operator>>(istream& in, pair<T1, T2>& p) {
  return in >> p.first >> p.second;
}

template<class T1, class T2>
ostream& operator<<(ostream& out, const pair<T1, T2>& p) {
  return out << p.first << ' ' << p.second;
}

template<size_t I = 0, typename... Ts>
typename enable_if<I == sizeof...(Ts), istream&>::type
read_tuple(istream& in, tuple<Ts...>& t) { return in; }

template<size_t I = 0, typename... Ts>
typename enable_if<I < sizeof...(Ts), istream&>::type
read_tuple(istream& in, tuple<Ts...>& t) {
  in >> get<I>(t);
  return read_tuple<I + 1>(in, t);
}

template<typename... Ts>
istream& operator>>(istream& in, tuple<Ts...>& t) {
  return read_tuple(in, t);
}

template<size_t I = 0, typename... Ts>
typename enable_if<I == sizeof...(Ts), void>::type
write_tuple(ostream& out, const tuple<Ts...>&) {}

template<size_t I = 0, typename... Ts>
typename enable_if<I < sizeof...(Ts), void>::type
write_tuple(ostream& out, const tuple<Ts...>& t) {
  if (I) out << ' ';
  out << get<I>(t);
  write_tuple<I + 1>(out, t);
}

template<typename... Ts>
ostream& operator<<(ostream& out, const tuple<Ts...>& t) {
  write_tuple(out, t);
  return out;
}

template<typename T>
istream& operator>>(istream& in, vector<T>& v) {
  for (auto& x : v) in >> x;
  return in;
}

template<typename T>
ostream& operator<<(ostream& out, const vector<T>& v) {
  for (size_t i = 0; i < v.size(); ++i)
    out << (i ? " " : "") << v[i];
  return out;
}

int n, a, b, f[300001], skibidi, ans = inf, dp[300001];
vector<int> adj[300001];
vector<pii> path;
pii x;

void dfs1(int u, int p) {
  f[u] = p;
  for (auto v: adj[u]) if (v != p) dfs1(v, u);
}

void dfs2(int u, int p) {
  for (auto v: adj[u]) if (v != p && make_pair(u, v) != x && make_pair(v, u) != x) dfs2(v, u);
  vector<int> vec;
  for (auto v: adj[u]) if (v != p && make_pair(u, v) != x && make_pair(v, u) != x) {
    vec.push_back(dp[v]);
  }
  sort(vec.begin(), vec.end(), greater<>());
  for (int i = 0; i < vec.size(); i++) dp[u] = max(dp[u], vec[i] + i + 1);
}

int calc(pii e) {
  x = e;
  memset(dp, 0, sizeof dp);
  dfs2(a, 0);
  dfs2(b, 0);
  return max(dp[a], dp[b]);
}

int main() {
  bruh;
  cin >> n >> a >> b;
  for (int i = 1; i < n; i++) {
    static int u, v; cin >> u >> v;
    adj[u].push_back(v);
    adj[v].push_back(u);
  }
  dfs1(a, 0); skibidi = b;
  while (f[skibidi] != 0) {
    path.push_back({skibidi, f[skibidi]});
    skibidi = f[skibidi];
  }
  int l = 0, r = path.size() - 1;
  while (l <= r) {
    int m1 = l + (r-l)/3, m2 = r - (r-l)/3;
    int f1 = calc(path[m1]), f2 = calc(path[m2]);
    if (f1 > f2) l = m1 + 1;
    else ans = f1, r = m2 - 1;
  }
  // cerr << path << '\n';
  cout << ans;
}

• Subtask 1: 0 / 31
• Subtask 2: 69 / 69