Submission #553917

#	Time	Username	Problem	Language	Result	Execution time	Memory
553917		Arvin	Colors (BOI20_colors)	C++11	0 / 100	0 ms	208 KiB

Colors

#include <bits/stdc++.h>

using namespace std;

#define ll long long

set<ll> st;
ll pos = 0, ans = 1e18;

bool ask(ll n){
	cout << "? " << n << endl;
	st.insert(n);
	
	int res;
	cin >> res;
	
	if(res){
		ans = min(ans, abs(n-pos));
	}
	pos = n;
	return (res == 1);
}

int main(){
	ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
	
	ll n;
	cin >> n;
	
	ans = n;
	if(n <= 64){
		ll l = 1, r = n+1;
		ask(1);
		for(int x=1;x<n;x++){
			if(x&1){
				r--;
				if(ask(r)){
					ans = min(ans, r-l);
				}
			} else {
				l++;
				if(ask(l)){
					ans = min(ans, r-l);
				}
			}
		}
		
		cout << "= " << ans << endl;
		return 0;
	}
	
	ll left = (n%2), right = n/2;
	while(left <= right){
		ll mid = (left+right) >> 1;
		
		ll pL = (n+1)/2-mid, pR = (n+1)/2+mid;
		ask(pL);
		if(ask(pR)){
			ans = min(ans, pR-pL);
			right = mid-1;
		} else {
			left = mid+1;
		}
	}
	
	int extra = 0;
	for(int i=1;i<=3;i++){
		bool valid = false;
		for(ll x=1;x<=n;x++){
			if(ans-i <= 0) break;
			if(!st.count(x) && !st.count(x+ans-i) && x+ans-i <= n){
				ask(x);
				if(ask(x+ans-i)){
					valid = true;
					extra++;
				}
				break;
			}
		}
		if(!valid) break;
	}
	
	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