Submission #1263781

#	Time	Username	Problem	Language	Result	Execution time	Memory
1263781		madamadam3	Migrations (IOI25_migrations)	C++20	30 / 100	47 ms	1820 KiB

migrations

#include "migrations.h"
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
using pi = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vi>;

void dfs(int u, int p, vi &dist, vvi &adj) {
  for (auto &v : adj[u]) {
    if (v == p) continue;
    dist[v] = dist[u] + 1;
    dfs(v, u, dist, adj);
  }
}

int furthest_from(int u, int n, vvi &adj) {
  vector<int> dist(n);
  dfs(u, u, dist, adj);

  int f = 0; for (int i = 0; i < n; i++) if (dist[i] > dist[f]) f = i;
  return f;
}

int dist_between(int n, int u, int v, vvi &adj) {
  vector<int> dist(n);
  dfs(u, u, dist, adj);

  return dist[v];
}

pi furthest_pair(int n, vvi &adj) {
  vector<int> dist(n);
  dfs(0, 0, dist, adj);
  int f1 = 0; for (int i = 0; i < n; i++) if (dist[i] > dist[f1]) f1 = i;
  dist = vi(n, 0);
  dfs(f1, f1, dist, adj);
  int f2 = 0; for (int i = 0; i < n; i++) if (dist[i] > dist[f2]) f2 = i;

  return {min(f1, f2), max(f1, f2)};
}

vi to_base(ll A, ll b, int pad = 0) {
  vi ans;
  while (A > 0LL) {
    ans.push_back(A % b);
    A /= b;
  }
  
  while (ans.size() < pad) ans.push_back(0);
  return ans;
}

ll from_base(vi bx, ll b) {
  ll po = 1;
  ll ans = 0;

  for (auto &el : bx) {
    ans += ll(el) * po;
    po *= b;
  }

  return ans;
}

vvi adj;
pi fr;
int diam = 0, cpos = 0;
int U = 0, V = 0, rU = 0, rV = 0;
vector<int> change_types;

int x = 0, actual_step = 0;
bool changed = false;
int send_message(int n, int i, int Pi) {
  if (i <= 1) adj.assign(n+1, vi());
  x = n - 30;

  adj[Pi].push_back(i);
  adj[i].push_back(Pi);

  if (i < x) return 0;
  int step = actual_step++;

  if (step == 0) {
    fr = furthest_pair(n, adj); diam = dist_between(n, fr.first, fr.second, adj); 
    U = fr.first; V = fr.second;
    rU = U, rV = V;
  } else if (step == 16) {
    rV = V = furthest_from(U, n, adj);
  }

  pi cfr = furthest_pair(n, adj);
  int u = cfr.first, v = cfr.second;
  int cdiam = dist_between(n, u, v, adj);

  int type = cdiam == diam ? 0 : (dist_between(n, i, V, adj) == cdiam ? 1 : 2); // if the diameter changed, did we switch u or v
  change_types.push_back(type);
  diam = cdiam;

  if (type == 1) U = i;
  else if (type == 2) V = i;

  vi u12 = to_base(rU, 12, 4), v2 = to_base(rV, 2, 14);
  if (step < 16 && !changed) {
    if (type == 0) {
      if (!((step % 4) == u12[step / 4] / 3)) return 0;
      return 1 + (u12[step / 4] % 3);
    } else {
      if (type == 2) U = V;

      changed = true;
      return 4;
    }
  } else if (step < 16 && changed) {
    if (!(step % 4 == 0 || step == 15)) return 0;

    int ans = 4;
    for (int k = 0; k < 4; k++) if (change_types[step - k] != 0) {ans = k; break;}
    return ans;
  } else if (step < 30) {
    if (type == 0) {
      return v2[min(13, step-16)];
    } else if (type == 1) {
      return v2[min(13, step-16)] + 2;
    } else {
      actual_step = 30;
      return 4;
    }
  } else {
    return type;
  }
}

// 0 - no change, 1 - change u, 2 - change v
pi longest_path(vi S) {
  int n = S.size();
  int x = n - 30;

  int u = 0, v = 0;
  // for (int i = x; i < x+16; i+=4) {
  //   for (int j = i; j < i + 4; j++) cout << S[j];
  //   cout << " ";
  // }
  // cout << "\n";

  int step = -1; bool changed = false;
  for (int i = x; i < n; i++) {
    step++;

    if (step < 16 && !changed) {
      if (S[i] == 4) {
        // cout << "step: " << step << " changed\n";
        u = i;
        changed = true;
        continue;
      }
      if (S[i] == 0) continue;

      int p12 = pow(12, step / 4);
      int v12 = 3 * (step % 4) + (S[i] - 1);

      u += p12 * v12;
    } else if (step < 16 && changed) {
      if (!(step % 4 == 0 || step == 15)) continue;
      if (S[i] == 4) continue;

      u = i - S[i];
    } else if (step < 30) {
      if (S[i] == 4) {
        step = 30;
        v = i;
      } else if (S[i] >= 2) {
        u = i;
        v += (S[i] - 2) * pow(2, step - 16);
      } else {
        v += S[i] * pow(2, step - 16);
      }
    } else {
      if (S[i] == 1) {
        u = i;
      } else if (S[i] == 2) {
        v = i;
      }
    }
  }

  // auto bp = furthest_pair(n, adj);
  // if (!(dist_between(n, u, v, adj) == dist_between(n, bp.first, bp.second, adj))) {
  //   cout << "failure!\n";
  // }
  int A = u, B = v;
  return {A, B}; 
}

• Subtask 0: 0 / 0
• Subtask 1: 30 / 30
• Subtask 2: 0 / 70