Submission #433189

#	Time	Username	Problem	Language	Result	Execution time	Memory
433189		Valaki2	Rack (eJOI19_rack)	C++14	100 / 100	13 ms	8064 KiB

rack

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

using ll = long long;

const ll mod = 1e9+7;

void solve() {
    ll n, k;
    cin >> n >> k;
    --k;
    vector<ll> powers_of_2_nomodulo(61, 0);
    vector<ll> powers_of_2(1 + n, 0);
    powers_of_2[0] = 1;
    powers_of_2_nomodulo[0] = 1;
    for(ll i = 1; i <= n; ++i) {
        powers_of_2[i] = (powers_of_2[i - 1] * 2) % mod;
    }
    for(ll i = 1; i <= 60; ++i) {
        powers_of_2_nomodulo[i] = powers_of_2_nomodulo[i - 1] * 2;
    }
    vector<bool> bits_of_k(1 + n, false);
    ll max_bit_of_k = 0;
    for(ll i = 0; i <= 60; ++i) {
        if(k & powers_of_2_nomodulo[i]) {
            bits_of_k[i] = true;
            max_bit_of_k = i;
        }
    }
    ll to_add = n - 1;
    ll where_we_are = 0;
    ll answer = 1;
    while(to_add >= 0) {
        if(bits_of_k[where_we_are]) {
            answer = (answer + powers_of_2[to_add]) % mod;
        }
        ++where_we_are;
        --to_add;
    }
    cout << answer << "\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}

Compilation message (stderr)

rack.cpp: In function 'void solve()':
rack.cpp:23:8: warning: variable 'max_bit_of_k' set but not used [-Wunused-but-set-variable]
   23 |     ll max_bit_of_k = 0;
      |        ^~~~~~~~~~~~

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