Ratsun reitit

#include <iostream>
#include <queue>
#include <unordered_map>
#include <vector>

static std::vector<size_t> neigh(int32_t x, int32_t y, int32_t len) {
  std::vector<size_t> retval;
  std::vector<std::pair<int32_t, int32_t>> diff = {
      {-1, 2}, {-1, -2}, {1, 2}, {1, -2}, {-2, 1}, {-2, -1}, {2, 1}, {2, -1}};
  for (auto pair : diff) {
    int32_t diff_x = pair.first;
    int32_t diff_y = pair.second;
    if (x + diff_x >= 0 && x + diff_x < len && y + diff_y >= 0 &&
        y + diff_y < len) {
      retval.push_back((x + diff_x) + (y + diff_y) * len);
    }
  }
  return retval;
}

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  size_t len;
  std::cin >> len;

  std::queue<size_t> q;
  q.push(0);
  std::vector<size_t> arr(len * len, SIZE_MAX);
  arr[0] = 0;

  while (!q.empty()) {
    size_t curr = q.front();
    q.pop();
    int32_t x = curr % len;
    int32_t y = curr / len;
    for (auto next : neigh(x, y, len)) {
      if (arr[next] == SIZE_MAX) {
        q.push(next);
        arr[next] = arr[curr] + 1;
      }
    }
  }

  for (size_t i = 0; i < len; ++i) {
    for (size_t j = 0; j < len; ++j) {
      std::cout << arr[i * len + j] << ' ';
    }
    std::cout << '\n';
  }
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

Test 6

Group: 1, 2, 3

Verdict: ACCEPTED

Test 7

Group: 1, 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: ACCEPTED

Test 9

Group: 2, 3

Verdict: ACCEPTED

Test 10

Group: 2, 3

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED