CSES - HIIT Open 2019 - Results
Submission details
Task:Bit Strings
Sender:Barely div 1
Submission time:2019-05-25 14:18:55
Language:C++
Status:READY
Result:ACCEPTED
Test results
testverdicttime
#1ACCEPTED0.03 sdetails
#2ACCEPTED0.02 sdetails
#3ACCEPTED0.06 sdetails
#4ACCEPTED0.02 sdetails
#5ACCEPTED0.06 sdetails
#6ACCEPTED0.05 sdetails
#7ACCEPTED0.02 sdetails
#8ACCEPTED0.05 sdetails
#9ACCEPTED0.05 sdetails
#10ACCEPTED0.06 sdetails
#11ACCEPTED0.09 sdetails
#12ACCEPTED0.01 sdetails
#13ACCEPTED0.10 sdetails
#14ACCEPTED0.11 sdetails
#15ACCEPTED0.10 sdetails
#16ACCEPTED0.11 sdetails
#17ACCEPTED0.12 sdetails
#18ACCEPTED0.12 sdetails

Code

#include <vector>
#include <iostream>
#include <algorithm>

using namespace std;
typedef long long LL;

vector<LL> cumsum { };
vector<LL> pows { };
vector<LL> nums { };

LL MOD = 1000000007;
int n,k;



LL norm(LL num) {
  while (num < 0) {
   num += MOD;
  }
  num = num % MOD;
  return num;
}

LL secondpow(LL pow) {
  if (pows.size() == 0) {
   pows.emplace_back(1);
   for (int i =0; i < 1000001; i++) {
     pows.emplace_back(norm(pows.back() * 2));
   }
  }
  return pows[pow];
}
int main() {
  cin >> n>>k;
  if (k == 1) {
    cout << 1 << endl;
    return 0;
  }  

  for (int i = 0; i < k; i++) {
    LL cur = secondpow(i);
    nums.emplace_back(cur);
  }
  
  cumsum = { 1 };
  for (int i = 1; i < k; i++) {
    LL ans = nums[i] + cumsum[i - 1];
    cumsum.emplace_back(norm(ans));
  }

//for (int i = 0; i < nums.size(); i++) cout << nums[i] << " "; cout<<endl;
//for (int i = 0; i < nums.size(); i++) cout << cumsum[i] << " "; cout<<endl;

  for (int i = k; i < n; i++) {
    LL previtem = (i == k) ? 0 : cumsum[i-k-1];
    LL newnum = cumsum.back() - previtem;
    nums.emplace_back(norm(newnum));
    LL newcumsum = norm(cumsum.back() + newnum);
    cumsum.emplace_back(newcumsum);
  }

//for (int i = 0; i < nums.size(); i++) cout << nums[i] << " "; cout<<endl;
//for (int i = 0; i < nums.size(); i++) cout << cumsum[i] << " "; cout<<endl;
  LL tmp = norm(secondpow(n) - nums.back());
  for (int i = nums.size() - k; i < n - 1; i++) {
    tmp = norm(tmp - nums[i]);
  }
  cout << norm(secondpow(n) - tmp);
  
}



Test details

Test 1

Verdict: ACCEPTED

input
1 1

correct output
1

user output
1

Test 2

Verdict: ACCEPTED

input
2 1

correct output
1

user output
1

Test 3

Verdict: ACCEPTED

input
2 2

correct output
3

user output
3

Test 4

Verdict: ACCEPTED

input
3 1

correct output
1

user output
1

Test 5

Verdict: ACCEPTED

input
3 2

correct output
5

user output
5

Test 6

Verdict: ACCEPTED

input
3 3

correct output
7

user output
7

Test 7

Verdict: ACCEPTED

input
4 1

correct output
1

user output
1

Test 8

Verdict: ACCEPTED

input
4 2

correct output
8

user output
8

Test 9

Verdict: ACCEPTED

input
4 3

correct output
13

user output
13

Test 10

Verdict: ACCEPTED

input
4 4

correct output
15

user output
15

Test 11

Verdict: ACCEPTED

input
654321 123456

correct output
796245691

user output
796245691

Test 12

Verdict: ACCEPTED

input
1000000 1

correct output
1

user output
1

Test 13

Verdict: ACCEPTED

input
1000000 10

correct output
256933600

user output
256933600

Test 14

Verdict: ACCEPTED

input
1000000 100

correct output
142013415

user output
142013415

Test 15

Verdict: ACCEPTED

input
1000000 1000

correct output
899626120

user output
899626120

Test 16

Verdict: ACCEPTED

input
1000000 10000

correct output
374265948

user output
374265948

Test 17

Verdict: ACCEPTED

input
1000000 100000

correct output
388134512

user output
388134512

Test 18

Verdict: ACCEPTED

input
1000000 1000000

correct output
235042058

user output
235042058