Submission #675665

#	Time	Username	Problem	Language	Result	Execution time	Memory
675665		a_aguilo	Rack (eJOI19_rack)	C++14	100 / 100	1 ms	212 KiB

rack

#include<bits/stdc++.h>

using namespace std;

unordered_map<long long, long long> powers;
const int MOD = 1e9+7;

long long int PowerTwo(long long int exponent){
    if(powers.find(exponent) != powers.end()) return powers[exponent];
    long long semiAns = PowerTwo(exponent/2);
    long long ans = (semiAns*semiAns)%MOD;
    if(exponent%2) {
        ans*= 2;
        ans%=MOD;
    }
    return powers[exponent] = ans;
}

long long getPos(long long int n, long long int k){
    if(k == 1) return 1;
    if(k%2){
        return getPos(n-1, k/2 +1);
    }
    else{
        long long semiAns = PowerTwo(n-1);
        long long ans = (semiAns + getPos(n-1, k/2))%MOD;
        return ans;
    }
}

int main(){
    powers[0] = 1;
    powers[1] = 2;
    powers[2] = 4;
    long long int n, k;
    cin >> n >> k;
    cout << getPos(n, k)<< endl;
    return 0;
}

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