Submission #1143500

#	Time	Username	Problem	Language	Result	Execution time	Memory
1143500		fryingduc	Rack (eJOI19_rack)	C++20	100 / 100	28 ms	34628 KiB

rack

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

#ifdef duc_debug
#include "bits/debug.h"
#else
#define debug(...)
#endif

const int maxn = 1e6 + 6;
const int mod = 1e9 + 7;
long long n, k;
int p[maxn];

long long calc(long long n, long long k) {
  if(n == 0) {
    return k;
  }
  long long ans = calc(n - 1, (k + 1) / 2) % mod;
  if(k % 2 == 0) {
    ans += p[n - 1];
    if(ans >= mod) ans -= mod;
  }
  return ans;
}

void solve() {
  cin >> n >> k;
  cout << calc(n, k);
}

signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  
  p[0] = 1;
  for(int i = 1; i < maxn; ++i) {
    p[i] = p[i - 1] + p[i - 1];
    if(p[i] >= mod) {
      p[i] -= mod;
    }
  }

  solve();

  return 0;
}

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