Submission #675726

#	Time	Username	Problem	Language	Result	Execution time	Memory
675726		Alma	Rack (eJOI19_rack)	C++17	40 / 100	1 ms	212 KiB

rack

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

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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    ll n, k;
    cin >> n >> k;
    ll pos = 1, add = n;
    bool inv = false;

    vector<int> powMOD(n+1);
    powMOD[0] = 1;
    for (int i = 1; i <= n; i++) {
        powMOD[i] = (powMOD[i-1] * 2) % MOD;
    }

    int i = 0;
    while (i < n) {
        if ((1 << i) > k) {
            inv = true;
            break;
        }
        add--;
        if (inv == false) {
            if ((k & (1 << i))) {
                inv = true;
            } else {
                pos += powMOD[add];
                pos %= MOD;
            }
        } else {
            if ((k & (1 << i))) {
                pos += powMOD[add];
                pos %= MOD;
            }
        }
        i++;
    }
    while (i < n) {
        add--;
        if (inv == false) {
            pos += powMOD[add];
            pos %= MOD;
        }
        i++;
    }
 
    cout << pos << '\n';

    return 0;
}

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