Submission #246139

#	Time	Username	Problem	Language	Result	Execution time	Memory
246139		proma	Rack (eJOI19_rack)	C++17	100 / 100	6 ms	384 KiB

rack

#include <bits/stdc++.h>
#define endl "\n"
#define int long long
#define see(x) cerr<<#x<<"="<<x<<endl;

using namespace std;

const int N = 1e6 + 10;
const int MOD = 1e9 + 7;

int bp (int n) {
    if (!n) return 1;
    if (n & 1) return 2ll * bp(n-1) % MOD;
    int b = bp(n>>1);
    return b * b % MOD;
}

int n, k, ans = 1;

int32_t main () {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    cin >> n >> k;
    k --;

    for (int i = n - 1; i >= 0; -- i)
        if (k & 1) {
            ans += bp(i);
            ans %= MOD;
            k >>= 1;
        }
        else k >>= 1;

    cout << ans << endl;

    return 0;
}

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