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<?php function combinations(int $n, int $k):array { function combine(int $n, int $k, int $start = 0, array &$result = [], array &$all = []) { if ($k == 0) { $all[] = $result; return; } for ($i = $start; $i <= $n - $k; $i++) { $result[$k] = $i; combine($n, $k - 1, $i + 1, $result, $all); } } $res = []; $all = []; combine($n, $k, 0, $res, $all); return $all; } function may_add_combination_to_set(array $combination, array $sets) { foreach ($sets as $combinationInSet) { if (count(array_intersect($combinationInSet, $combination)) !== 1) { return false; } } return true; } $combinations = combinations(31, 6); $sets = []; foreach ($combinations as $combination) { if (may_add_combination_to_set($combination, $sets)) { $sets[] = $combination; } } count($sets);
Output for 7.2.0 - 7.2.8, 7.2.29 - 7.2.33, 7.3.16 - 7.3.31, 7.4.0 - 7.4.33, 8.0.0 - 8.0.12, 8.0.14 - 8.0.30, 8.1.0 - 8.1.1, 8.1.28, 8.2.18, 8.3.5 - 8.3.6
Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 20480 bytes) in /in/vq7d6 on line 14
Process exited with code 255.
Output for 8.3.0 - 8.3.4
Fatal error: Out of memory (allocated 27262976 bytes) (tried to allocate 2097160 bytes) in /in/vq7d6 on line 9 mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.
Output for 8.2.0 - 8.2.17
Fatal error: Out of memory (allocated 31461376 bytes) (tried to allocate 20480 bytes) in /in/vq7d6 on line 14 mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.
Output for 8.1.2 - 8.1.27
Fatal error: Out of memory (allocated 29364224) (tried to allocate 4194312 bytes) in /in/vq7d6 on line 9 mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.
Output for 8.0.13
Fatal error: Out of memory (allocated 130027520) (tried to allocate 20480 bytes) in /in/vq7d6 on line 14 mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.
Output for 7.3.32 - 7.3.33
Fatal error: Out of memory (allocated 130027520) (tried to allocate 4096 bytes) in /in/vq7d6 on line 14 mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.
Output for 7.2.11

Process exited with code 137.
Output for 7.0.0 - 7.0.20, 7.1.0 - 7.1.20
Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 4096 bytes) in /in/vq7d6 on line 14
Process exited with code 255.
Output for 5.5.24 - 5.5.35, 5.6.8 - 5.6.28
Parse error: syntax error, unexpected ':', expecting '{' in /in/vq7d6 on line 4
Process exited with code 255.
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