Submission #216711

#	Time	Username	Problem	Language	Result	Execution time	Memory
216711		MODDI	Rack (eJOI19_rack)	C++14	100 / 100	17 ms	8684 KiB

rack

#include <bits/stdc++.h>
using namespace std;
int MOD= 1e9 + 7;
int main()
{
	long long n, k;
	cin>>n>>k;
	vector<long long> pow_two;
	pow_two.push_back(1);
	long long at=1;
	for(int i=1;i<n;i++)
	{
		at*=2;
		at %= MOD;
		if(at < 0)
			return 0;
		pow_two.push_back(at);
	}
	long long rez=1;
	long long step=1;
	while(k!=1)
	{
		if(k%2==0)
		{
			rez+=pow_two[n-step];
			rez %= MOD;
			if(rez < 0)
				return 0;
			k-=k/2;
			step++;
		}
		else {
			step++;
			k-=k/2;
		}
	}
	cout<<rez<<endl;
	return 0;
}

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 60 / 60