Submission #116293

#	Time	Username	Problem	Language	Result	Execution time	Memory
116293		user202729	The Big Prize (IOI17_prize)	C++17	97.12 / 100	67 ms	512 KiB

prize

// https://oj.uz/problem/view/IOI17_prize
#include "prize.h"
#include<array>

// simple wrapper over ask
std::array<int,2> sk(int x){
	auto v=ask(x);
	return {{v[0],v[1]}};
}

int maxsk;

int f(int l,std::array<int,2> lp,int r,std::array<int,2> rp){
	// return -1 if not found inside ]l..r[ , else index

	while(l+1<r&&lp[0]+lp[1]<maxsk){ // there are at most ~500 such element (non-lollipop) in total
		++l;
		lp=sk(l);
		if(lp[0]+lp[1]==0)return l;
	}
	while(r-1>l&&rp[0]+rp[1]<maxsk){
		--r;
		rp=sk(r);
		if(rp[0]+rp[1]==0)return r;
	}

	if(l+1==r)return -1;
	if(lp==rp)return -1; // [l] == [r], and no number > l or r in range
	int mid=(l+r)/2;
	auto mp=sk(mid);
	if(mp[0]+mp[1]==0)return mid;

	int res=f(l,lp,mid,mp);
	if(res>=0)return res;
	return f(mid,mp,r,rp);
}

int find_best(int n) {
	maxsk=0;
	std::array<std::array<int,2>,500> z;
	for(int i=std::min(500,n);i--;){
		z[i]=sk(i);
		maxsk=std::max(maxsk,z[i][0]+z[i][1]);
	}
	return f(-1,{0,n},n,{n,0});
}

• Subtask 1: 20 / 20
• Subtask 2: 77.12 / 80