Submission #999796

#	Time	Username	Problem	Language	Result	Execution time	Memory
999796		vjudge1	Rack (eJOI19_rack)	C++17	100 / 100	3 ms	348 KiB

rack

#include <bits/stdc++.h>
using namespace std;
#define mod 1000000007
#define ll unsigned long long
ll binpow(ll a, ll b){
    ll res = 1;
    while(b != 0){
        if (b % 2 == 0){
            b /= 2;
            a *= a;
            a %= mod;
        }
        else{
            b--;
            res *= a;
            res %= mod;
        }
    }
    return res;
}
ll f(ll n, ll k, ll va){
    va %= mod;
    ll ans = 0;
    if (n == 0){
        return 0;
    }
    if (n <= 63){
        ll ag = pow(2ull, n - 1);
        if (ag < k){
            ans += va;
            ans += f(n - 1, k - ag, va * 2);
            return ans;
        }
    }
    ans += f(n - 1, k, va * 2);
    return ans;
}
int main(){
    ll n, k;
    cin>>n>>k;
    cout<<(f(n, k, 1) + 1) % mod;
}

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