Counter

#include <iostream>
#include <cstring>
#include <queue>

const int N = 1e6 + 5;

int x;
int f[N];

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  std::memset(f, 0x3f, sizeof(f));
  std::cin >> x;
  std::priority_queue<std::pair<int, int>> pq;
  f[0] = 0;
  pq.push({-f[0], 0});
  while (!pq.empty()) {
    int cd = -pq.top().first;
    int u = pq.top().second;
    pq.pop();
    if (cd != f[u]) {
      continue;
    }
    if (0 <= u - 2 && u - 2 <= x) {
      if (f[u - 2] > f[u] + 1) {
        f[u - 2] = f[u] + 1;
        pq.push({-f[u - 2], u - 2});
      }
    }
    if (0 <= u + 11 && u + 11 <= x) {
      if (f[u + 11] > f[u] + 1) {
        f[u + 11] = f[u] + 1;
        pq.push({-f[u + 11], u + 11});
      }
    }
  }
  std::cout << (f[x] == 0x3f3f3f3f ? -1 : f[x]) << '\n';
  return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED