Submission #553816

#	Time	Username	Problem	Language	Result	Execution time	Memory
553816		Arvin	Colors (BOI20_colors)	C++11	0 / 100	1 ms	208 KiB

Colors

#include <bits/stdc++.h>

using namespace std;

#define ll long long

set<ll> st;

bool ask(ll n){
	cout << "? " << n << endl;
	
	st.insert(n);
		
	int res;
	cin >> res;
	
	return (res == 1);
}

int main(){
	ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
	
	ll n;
	cin >> n;
	
	ll ans = n;
	ll pos = (n+1)/2;
	ask(pos);
	
	ll cur = 1;
	ll left = 1, right = n-1;
	while(left <= right){
		ll mid = (left+right) >> 1;
		
		while(st.count(cur)){
			cur++;
		}
		
		bool valid = false;
		if(pos-mid > 0 && !st.count(pos-mid)){
			if(ask(pos-mid)){
				valid = true;
			} else {
				valid = false;
			}
			pos -= mid;
		} else if(pos+mid <= n && !st.count(pos+mid)){
			if(ask(pos+mid)){
				valid = true;
			} else {
				valid = false;
			}
			pos += mid;
		} else {
			ask(cur);
			pos = cur;
			
			if(ask(pos+mid)){
				valid = true;
			} else {
				valid = false;
			}
			pos += mid;
		}
		
		if(valid){
			ans = mid;
			right = mid-1;
		} else {
			left = mid+1;
		}
	}
	
	cout << "= " << ans << endl;
    return 0;
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 13
• Subtask 3: 0 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 33