Submission #428824

#	Time	Username	Problem	Language	Result	Execution time	Memory
428824		errorgorn	Park (JOI17_park)	C++17	10 / 100	1323 ms	836 KiB

park

#include "park.h"

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ii pair<ll,ll>
#define fi first
#define se second
#define endl '\n'

#define puf push_front
#define pof pop_front
#define pub push_back
#define pob pop_back
#define lb lower_bound
#define ub upper_bound

#define rep(x,s,e) for (auto x=s-(s>e);x!=e-(s>e);s<e?x++:x--)
#define all(x) (x).begin(),(x).end()
#define sz(x) (int) (x).size()

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

int t,n;

int Ask(int i,int j,vector<int> v){
	//cout<<"Ask: "<<i<<" "<<j<<" | "; for (auto &it:v) cout<<it<<" "; cout<<endl;
	
	if (i>j) swap(i,j); //the fuck?
	
	int arr[n];
	memset(arr,0,sizeof(arr));
	
	for (auto &it:v) arr[it]^=1;
	return Ask(i,j,arr);
}

void ans(int i,int j){
	if (i>j) swap(i,j);
	
	Answer(i,j);
}

void rec(vector<int> v){
	//cout<<"debug: "; for (auto &it:v) cout<<it<<" "; cout<<endl;
	
	if (sz(v)==1) return;
	
	//try to make pivot the centroid	
	shuffle(all(v),rng);
	
	int root=v[sz(v)-1];
	
	//high chance this is a descendant of the centroid
	int pivot=v[sz(v)-2];
	
	//we can try to find parents of the current pivot?
	vector<int> par;
	
	for (auto &it:v){
		if (it==root) continue;
		if (it==pivot){
			par.pub(it);
			continue;
		}
		
		vector<int> vv=v;
		vv.pub(it);
		if (Ask(root,pivot,vv)==0) par.pub(it);
	}
	
	while (sz(par)!=1){
		int temp=par[rng()%sz(par)];
		set<int> spar;
		for (auto &it:par) spar.insert(it);
		vector<int> lower,upper;
		int subsize=0;
		
		for (auto &it:v){
			if (it==root) continue;
			if (it==temp) continue;
			
			vector<int> vv=v;
			vv.pub(temp);
			if (Ask(root,it,vv)==0){
				subsize++;
				if (spar.count(it)) lower.pub(it);
			}
			else{
				if (spar.count(it)) upper.pub(it);
			}
		}
		
		if (subsize>sz(v)/2){
			par=lower;
			if (par.empty()) par.pub(temp);
		}
		else{
			par=upper;
			if (par.empty()) par.pub(root);
		}
	}
	
	pivot=par[0];
	
	rep(x,0,sz(v)) if (v[x]==pivot) swap(v[x],v.back());
	v.pob();
	
	while (sz(v)){
		vector<int> split;
		vector<int> rest;
		
		split.pub(v.back());
		
		for (auto &it:v){
			if (it==split[0]) continue;
			
			if (Ask(split[0],it,v)==1) split.pub(it);
			else rest.pub(it);
		}
		
		//now we need to find how split is connected to pivot
		vector<int> cset={pivot};
		int connect;
		for (auto &it:split){
			cset.pub(it);
			if (Ask(it,pivot,cset)){
				ans(it,pivot);
				connect=it;
				break;
			}
		}
		
		rec(split);
		
		v=rest;
	}
}

void Detect(int T, int N) {
	t=T,n=N;
	
	if (t==1){
		rep(x,0,n) rep(y,x+1,n){
			if (Ask(x,y,{x,y})==1) Answer(x,y);
		}
	}
	else{
		vector<int> proc;
		rep(x,0,n) proc.pub(x);
		
		rec(proc);
	}
}

Compilation message (stderr)

park.cpp: In function 'void rec(std::vector<int>)':
park.cpp:125:7: warning: variable 'connect' set but not used [-Wunused-but-set-variable]
  125 |   int connect;
      |       ^~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 27
• Subtask 4: 0 / 30
• Subtask 5: 0 / 23