Submission #675712

#	Time	Username	Problem	Language	Result	Execution time	Memory
675712		Alma	Rack (eJOI19_rack)	C++17	40 / 100	1 ms	328 KiB

rack

#include <bits/stdc++.h>
using namespace std;

using ll = long long;
ll MOD = 1e9+7;

ll calcMODpow(int b, int p) {
    if (p == 0) return 1;
    ll x = calcMODpow(b, p/2);
    if (p % 2 == 1) {
        return (((x*x) % MOD)*b) % MOD;
    } else {
        return (x*x) % MOD;
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    
    ll n, k;
    cin >> n >> k;
    ll pos = 1, add = n;
    bool inv = false;

    for (ll i = 0; i < min(n, 1LL * 60); i++) {
        add--;
        if (inv == false) {
            if ((k & (1 << i))) {
                inv = 1;
            } else {
                pos += calcMODpow(2, add);
                pos %= MOD;
            }
        } else {
            if ((k & (1 << i))) {
                pos += calcMODpow(2, add);
                pos %= MOD;
            } else {
                inv = true;
            }
        }
    }

    cout << pos << '\n';

    return 0;
}

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 0 / 60