Submission #1334504

#TimeUsernameProblemLanguageResultExecution timeMemory
1334504sporknivesRarest Insects (IOI22_insects)C++20
10 / 100
106 ms428 KiB
#include <bits/stdc++.h>
#include "insects.h"
using namespace std;

// determine no. of groups and 1st insect in each grp - around n cost
// with m groups the answer is at most n/m
// repeat but remove the 1st in each group to find the 2nd in each group
// this method lets us find the size of smallest grp in O(smallest grp size * n) = O(n^2/m)
// alternatively, find the elements of the largest grp in O(n), repeat for every group = O(nm)
// small/large split gives O(nsqrtn)
int min_cardinality(int N) {
	int m = 0;
	bool marked[N]; memset(marked,false,sizeof(marked));
	vector<int> to_remove;
	for(int i=0;i<N;i++) {
		move_inside(i);
		int res = press_button();
		if(res>1) {
			move_outside(i);
		}
		else {
			m++;
			marked[i]=true;
			to_remove.push_back(i);
		}
	}
	
	for(int x: to_remove) move_outside(x);
	to_remove.clear();
	
	if(m>=25) {
		int ans=1;
		while(true) {
			int cnt=0;
			for(int i=0;i<N;i++) {
				if(marked[i])continue;
				move_inside(i);
				int res = press_button();
				if(res>1) {
					move_outside(i);
				}
				else {
					cnt++;
					marked[i]=true;
					to_remove.push_back(i);
				}
			}
			
			if(cnt<m) {
				return ans;
			}
			ans++;
			
			for(int x: to_remove) move_outside(x);
			to_remove.clear();
		}
	}
	else {
		int ans=INT_MAX;
		bool marked2[N]; memset(marked2,false,sizeof(marked2));
		while(true) {
			for(int i=0;i<N;i++) {
				if(!marked2[i])move_inside(i);
			}
			int sz = press_button();
			if(sz==0) break;
			int idx = 0;
			for(int i=0;i<N;i++) {
				move_outside(i);
				int res=press_button();
				//cout<<res<<"\n";
				if(res<sz) {
					idx=i;
					break;
				}
			}
			
			for(int i=idx+1;i<N;i++) move_outside(i);
			move_inside(idx);
			marked2[idx]=true;
			for(int i=idx+1;i<N;i++) {
				move_inside(i);
				int res=press_button();
				if(res==2) {
					marked2[i]=true;
				}
				move_outside(i);
			}
			move_outside(idx);
			ans=min(ans,sz);
			
			//for(int i=0;i<N;i++) cout<<marked2[i]<<" ";
			//cout<<"\n";
		}
		return ans;
	}
}
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