Submission #1240469

#	Time	Username	Problem	Language	Result	Execution time	Memory
1240469		mychecksedad	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	8 ms	420 KiB

longesttrip

#include "longesttrip.h"
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define all(x) x.begin(),x.end()
#define vi vector<int>
#define pii pair<int,int>
#define ff first
#define ss second

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int rn(int l, int r){
  return uniform_int_distribution<int>(l,r)(rng);
}

int ask(int u, int v){
  return are_connected(vi{u}, vi{v});
}

std::vector<int> longest_trip(int n, int D){
  vi p;
  for(int i = 1; i <= n; ++i){
    p.pb(i-1);
    swap(p[i-1], p[rn(0, i-1)]);
  }

  vi A, B;
  A.pb(p[0]);
  for(int i = 1; i < n; ++i){
    int v = p[i];
    int u = A.back();
    if(ask(u, v)){
      A.pb(v);
    }else if(B.size()){
      u = B.back();
      if(ask(u, v)){
        B.pb(v);
      }else{
        reverse(all(B));
        for(int x: B) A.pb(x);
        B.clear();
        B.pb(v);
      }
    }else B.pb(v);
  }
  if(B.size()>A.size()) A.swap(B);
  if(B.empty()) return A; 
  int x = B[0], y = B.back();
  int x1 = A[0], y1 = A.back();

  bool ok = ask(x, x1);
  bool ok1 = ask(x, y1);

  if(ok){
    reverse(all(A));
    for(int x: B) A.pb(x);
    return A;
  }
  if(ok1){
    for(int x: B) A.pb(x);
    return A;
  }

  ok = ask(y, x1);
  ok1 = ask(y, y1);

  if(ok){
    for(int x: A) B.pb(x);
    return B;
  }
  if(ok1){
    reverse(all(A));
    for(int x: A) B.pb(x);
    return B;
  }

  // we got two loops

  if(are_connected(A, B)){
    // full path
    int l = 0, r = int(A.size())-2, res = int(A.size())-1;
    while(l <= r){
      int mid = l+r>>1;
      vi AA;
      for(int j = 0; j <= mid; ++j) AA.pb(A[j]);
      if(are_connected(AA, B)){
        res = mid;
        r = mid-1;
      }else{
        l = mid + 1;
      }
    }
    int i = res;
    
    l = 0, r = int(B.size())-2, res = int(B.size())-1;
    while(l <= r){
      int mid = l+r>>1;
      vi BB;
      for(int j = 0; j <= mid; ++j) BB.pb(B[j]);
      if(are_connected(vi{A[i]}, BB)){
        res = mid;
        r = mid-1;
      }else{
        l = mid + 1;
      }
    }
    int j = res;
    vi ress;
    for(int k = i + 1; k < B.size(); ++k) ress.pb(B[k]);
    for(int k = 0; k <= i; ++k) ress.pb(B[k]);
    for(int k = j; k < A.size(); ++k) ress.pb(A[k]);
    for(int k = 0; k < j; ++k) ress.pb(A[k]);
    return ress;
  }


  return A;
}

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 60