Submission #1100436

#	Time	Username	Problem	Language	Result	Execution time	Memory
1100436		biank	Rack (eJOI19_rack)	C++14	100 / 100	4 ms	8020 KiB

rack

#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const int MOD = 1e9 + 7;
const int MAX_N = 1e6;

ll pot[MAX_N];

int solve(int n, ll k) {
    if (n == 0) return 1LL;
    if (k % 2 == 1) return solve(n - 1, (k + 1) / 2);
    int res = pot[n - 1] + solve(n - 1, k / 2);
    if (res >= MOD) res -= MOD;
    return res;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
	
    int n;
    ll k;
    cin >> n >> k;
    pot[0] = 1;
    for (int i = 1; i < n; i++) {
        pot[i] = 2 * pot[i - 1];
        if (pot[i] >= MOD) pot[i] -= MOD;
    }
    cout << solve(n, k) << '\n';
    
    return 0;
}

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