Submission #573916

#	Time	Username	Problem	Language	Result	Execution time	Memory
573916		lumibons	Flight to the Ford (BOI22_communication)	C++17	26.40 / 100	4809 ms	2052 KiB

communication

#include <vector>
#include <cstdlib>
#include "communication.h"

typedef long long ll;

using namespace std;

struct interval {
  ll l, r;
  interval(ll l, ll r) : l(l), r(r) {}
  bool contains(ll x) {
    return l <= x && x < r;
  }
  ll length() {
    return r - l;
  }
  interval shrink(ll o, ll s) {
    return interval(min(r, l + o), min(r, l + o + s));
  }
};

vector<interval> splitIntervals(vector<interval> c, ll o, ll s) {
  vector<interval> r;
  for (interval &it : c) {
    if (s > 0 && it.length() - o > 0)
      r.push_back(it.shrink(o, s));
    s -= max(0LL, min(s, it.length() - o));
    o -= min(o, it.length());
  }
  return r;
}

bool contains(vector<interval> c, ll x) {
  for (interval &it : c)
    if (it.contains(x))
      return true;
  return false;
}

struct state {
  ll s = 0;
  vector<interval> c;
  state() {}
  state(ll N): s(N) {
    c.emplace_back(1, N + 1);
  }
  state(vector<vector<interval>> &cs) {
    for (vector<interval> &c : cs)
      add(c);
  }
  void add(interval it) {
    s += it.length();
    c.push_back(it);
  }
  void add(vector<interval> &c) {
    for (interval &it : c)
      add(it);
  }
  vector<vector<interval>> split(int n) {
    vector<vector<interval>> r;
    ll o = 0, rs = s;
    for (int i = 0; i < n; i++) {
      ll cs = rs / (n - i);
      rs -= cs;
      r.push_back(splitIntervals(c, o, cs));
      o += cs;
    }
    return r;
  }
  ll size() {
    return s;
  }
  vector<ll> remaining() {
    vector<ll> r;
    for (interval &it : c)
      for (ll v = it.l; v < it.r; v++)
        r.push_back(v);
    return r;
  }
};

void reduce(state &s, int ps, const vector<int> &p, int X = -1) {
  // if (rand() & 1)
  //   X != -1 ? send(0) : receive();
  int rp = 0, pc = (int) p.size();
  vector<vector<interval>> c = s.split(pc);
  int sp = 0;
  while (X != -1 && !contains(c[sp], X))
    sp++;
  for (int i = 0; i < ps; i++)
    rp |= (X != -1 ? send((p[sp] >> i) & 1) : receive()) << i;
  vector<vector<interval>> nc;
  for (int i = 0; i < pc; i++)
    if (((p[i] ^ rp) & ((p[i] ^ rp) >> 1)) == 0)
      nc.push_back(c[i]);
  s = state(nc);
}

std::pair<int, int> solve(int N, int X = -1) {
  state s(N);
  srand(42);

  // for (int ps = 10; ps >= 4; ps -= 2) {
  //    vector<int> p;
  //    for (int i = 0; i < (1 << ps); i++)
  //      p.push_back(i);
  //    while (s.size() >= (int) p.size())
  //      reduce(s, ps, p, X);
  // }
  // -> 106, ok

  // int ps = 10;
  // vector<int> p;
  // for (int i = 0; i < (1 << ps); i++)
  //   p.push_back(i);
  // while (s.size() >= (int) p.size())
  //   reduce(s, ps, p, X);
  // -> 108, ok

  while (s.size() >= 6)
    reduce(s, 5, {0, 3, 12, 17, 10, 31}, X); // -> 224, ok
    // reduce(s, 4, {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}, X); // -> 116, ok
    // reduce(s, 4, {1, 2, 4, 15}, X); // -> >250, ok
    // reduce(s, 4, {0, 7, 9, 15}, X); // -> >250, ok

  while (s.size() > 2)
    reduce(s, 4, {0, 6, 9, 15}, X);

  vector<ll> r = s.remaining();
  return {r[0], r.back()};
}

void encode(int N, int X) {
  solve(N, X);
}

std::pair<int, int> decode(int N) {
  return solve(N);
}

• Subtask 1: 15 / 15
• Subtask 2: 11.40003 / 85