Submission #1262543

#	Time	Username	Problem	Language	Result	Execution time	Memory
1262543		madamadam3	Migrations (IOI25_migrations)	C++20	0 / 100	37 ms	1204 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;

bool gone_down = false;

int x = 0, actual_step = 0;
int send_message(int n, int i, int Pi) {
  if (i <= 1) adj.assign(n+1, vi());
  x = n - 21;

  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 == 7 && !gone_down) {
    rV = V = furthest_from(U, n, adj);
    gone_down = true;
  }

  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
  diam = cdiam;

  if (type == 1) U = i;
  else if (type == 2) V = i;
  
  vi u4 = to_base(rU, 4, 7), v2 = to_base(rV, 2, 14);
  if (step < 7) {
    if (type == 0) {
      return u4[step];
    } else if (type == 1) {
      actual_step = 7;
      return 4;
    } else {
      U = V; actual_step = 7;
      return 4;
    }
  } else if (step < 21) {
    
    if (type == 0) {
      return v2[step-7];
    } else if (type == 1) {
      return v2[step-7] + 2;
    } else {
      actual_step = 21;
      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 - 21;

  int u = 0, v = 0;
  vector<pi> switches; // idx, 0 if u, 1 if v

  int step = 0;
  for (int i = x; i < n; i++) {
    if (step < 7) {
      if (S[i] == 4) {
        u = i; step = 7;
        continue;
      } else {
        u += S[i] * pow(4, step);
      }
    } else if (step < 21) {
      if (S[i] == 4) {
        step = 21;
        v = i;
      } else if (S[i] >= 2) {
        u = i;
        v += (S[i] - 2) * pow(2, step - 7);
      } else {
        v += S[i] * pow(2, step - 7);
      }
    } else {
      if (S[i] == 1) {
        v = i;
      } else if (S[i] == 2) {
        u = i;
      }
    }

    step++;
  }

  int A = u, B = v;

  // for (auto &el : switches) {
  //   int w = el.first;
  //   if (el.second) { // joining
  //     B = w;
  //   } else { // extending
  //     A = w;
  //   }
  // }

  return {A, B}; 
}

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