Submission #986806

#	Time	Username	Problem	Language	Result	Execution time	Memory
986806		arush_agu	Cat Exercise (JOI23_ho_t4)	C++17	54 / 100	213 ms	131900 KiB

Main

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#ifdef DEBUG
#include <time.h>
#endif

#define all(a) (a).begin(), (a).end()
#define rev(a) (a).rbegin(), (a).rend()
#define F first
#define S second
int recur_depth = 0;
#ifdef DEBUG
#define dbg(x)                                                                 \
  {                                                                            \
    ++recur_depth;                                                             \
    auto x_ = x;                                                               \
    --recur_depth;                                                             \
    cerr << string(recur_depth, '\t') << "\e[91m" << __func__ << ":"           \
         << __LINE__ << "\t" << #x << " = " << x_ << "\e[39m" << endl;         \
  }
#else
#define dbg(x)
#endif

using namespace std;
using namespace __gnu_pbds;

typedef pair<int, int> ii;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> llll;

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pair<int, int>> vii;
typedef vector<vii> vvii;

typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pair<ll, ll>> vll;
typedef vector<vll> vvll;

typedef vector<bool> vb;

template <class type1>
using ordered_set = tree<type1, null_type, less<type1>, rb_tree_tag,
                         tree_order_statistics_node_update>;

template <typename A, typename B>
ostream &operator<<(ostream &os, const pair<A, B> &p) {
  return os << '(' << p.first << ", " << p.second << ')';
}
template <typename T_container, typename T = typename enable_if<
                                    !is_same<T_container, string>::value,
                                    typename T_container::value_type>::type>
ostream &operator<<(ostream &os, const T_container &v) {
  os << '{';
  string sep;
  for (const T &x : v)
    os << sep << x, sep = ", ";
  return os << '}';
}

const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
const ll INF = 1e9;
const ld EPS = 1e-9;

template<typename T>
struct ST {
  const int MAXLG = 22;

  int n;
  vector<vector<T>> st;
  vi lg2;

  ST(int n, vector<T>& a) : n(n) {
    st = vector<vector<T>>(MAXLG, vector<T>(n));
    for (int i=0; i<n; i++) st[0][i] = a[i];

    for (int j=1; j<MAXLG; j++) for (int i=0; i + (1 << j) <= n; i++) 
      st[j][i] = min(st[j - 1][i], st[j - 1][i + (1 << (j - 1))]);

    lg2 = vi(n + 10);
    for (int i=2; i<n + 10; i++) lg2[i] = lg2[i / 2] + 1;
  }

  T query(int l, int r) {
    if (l > r) swap(l, r);
    int k = lg2[r - l + 1];
    return min(st[k][l], st[k][r - (1 << k) + 1]);
  }
};

struct DSU {
  int n;
  vi par, sz, mx;

  DSU(int n) : n(n), par(vi(n, -1)), sz(vi(n, 1)) {
    mx = vi(n);
    for (int i=0; i<n; i++) mx[i] = i;
  }

  int find(int x) {
    if (par[x] == -1) return x;
    return par[x] = find(par[x]);
  }

  void merge(int u, int v) {
    u = find(u), v = find(v);
    if (u == v) return;

    if (sz[v] > sz[u]) swap(u, v);
    par[v] = u;
    sz[u] += sz[v];
    mx[u] = max(mx[u], mx[v]);
  }
};

void solve() {
  int n; cin >> n;
  vi p(n); for (int &x : p) cin >> x, x--;
  vvi adj(n);
  vii ed(n - 1);
  for (int i=0; i<n - 1; i++) {
    cin >> ed[i].first >> ed[i].second;
    ed[i].first--, ed[i].second--;
    adj[ed[i].first].push_back(ed[i].second);
    adj[ed[i].second].push_back(ed[i].first);
  }

  vi inv_p(n);
  for (int i=0; i<n; i++) inv_p[p[i]] = i;

  sort(all(ed), [&](ii a, ii b) {
    return max(p[a.first], p[a.second]) < max(p[b.first], p[b.second]);
  });

  int idx_n = find(all(p), n - 1) - p.begin();

  vi depth(n), idx(n);
  vii euler;
  function<void(int, int)> f = [&](int u, int p) {
    idx[u] = euler.size();
    euler.push_back({depth[u], u});
    for (int &v : adj[u]) if (v != p) {
      depth[v] = depth[u] + 1;
      f(v, u);
      euler.push_back({depth[u], u});
    }
  }; f(idx_n, -1);

  ST st(euler.size(), euler);
  DSU dsu(n);

  auto dist = [&](int u, int v) {
    int lca = st.query(idx[u], idx[v]).second;
    return depth[u] + depth[v] - 2 * depth[lca];
  };

  vvi nadj(n);
  for (auto &[ui, vi] : ed) {
    int u = p[ui], v = p[vi];
    int u_max = dsu.mx[dsu.find(u)], v_max = dsu.mx[dsu.find(v)];

    nadj[u_max].push_back(v_max);
    nadj[v_max].push_back(u_max);
    dsu.merge(u, v);
  }

  int ans = 0;
  function<void(int, int, int)> g = [&](int u, int p, int tot) {
    if (p != -1)
      tot += dist(inv_p[u], inv_p[p]);
    ans = max(ans, tot);
    for (int &v : nadj[u]) if (v != p)
      g(v, u, tot);
  }; g(n - 1, -1, 0);

  cout << ans << "\n";
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);

  clock_t start = clock();

  int test_cases = 1;
  // cin >> test_cases;

  while (test_cases--)
    solve();

#ifdef DEBUG
  cerr << fixed << setprecision(10)
       << "\nTime Taken: " << (double)(clock() - start) / CLOCKS_PER_SEC
       << "s\n";
#endif
  return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:213:11: warning: unused variable 'start' [-Wunused-variable]
  213 |   clock_t start = clock();
      |           ^~~~~

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 0 / 20
• Subtask 6: 23 / 23
• Subtask 7: 0 / 26