Nyanten

Nyanten is a C++ library for fast calculation of deficiency number (a.k.a. shanten number, 向聴数).

Typical Usage

#include <nyanten/replacement_number.hpp>

int main()
{
  std::vector<unsigned> hand;
  // Set the count of each tile to `hand`.
  unsigned const replacement_number = Nyanten::calculateReplacementNumber(hand);
}

Interfaces

template<typename ForwardIterator>
std::uint_fast8_t Nyanten::calculateReplacementNumber(ForwardIterator first, ForwardIterator last)

Preconditions

• std::distance(first, last) == 34
• For every iter in the range [first, last), 0 <= *iter and *iter <= 4
• The sum of the numbers in the range [first, last) is less or equal to 14.
• The sum of the numbers in the range [first, last) is congruent to 1 or 2 modulo 3.

Effects

Calculate the replacement number, which is equal to the deficiency number (a.k.a. Shanten number, 向聴数) plus one. The hand is represented by the range [first, last). Each element of the range corresponds to the count of each tile type. If there are melds (副露), the count must exclude the melded tiles. The correspondence between the element indices of the range and the tile types is as shown in the table below.

Index	0	1	2	3	4	5	6	7	8
Tile	🀇 (1m)	🀈 (2m)	🀉 (3m)	🀊 (4m)	🀋 (5m)	🀌 (6m)	🀍 (7m)	🀎 (8m)	🀏 (9m)

Index	9	10	11	12	13	14	15	16	17
Tile	🀙 (1p)	🀚 (2p)	🀛 (3p)	🀜 (4p)	🀝 (5p)	🀞 (6p)	🀟 (7p)	🀠 (8p)	🀡 (9p)

Index	18	19	20	21	22	23	24	25	26
Tile	🀐 (1s)	🀑 (2s)	🀒 (3s)	🀓 (4s)	🀔 (5s)	🀕 (6s)	🀖 (7s)	🀗 (8s)	🀘 (9s)

Index	27	28	29	30	31	32	33
Tile	🀀 (E)	🀁 (S)	🀂 (W)	🀃 (N)	🀆 (White)	🀅 (Green)	🀄 (Red)

template<typename ForwardRange>
std::uint_fast8_t Nyanten::calculateReplacementNumber(ForwardRange const &r)

Call Nyanten::calculateReplacementNumber(std::cbegin(r), std::cend(r)).