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Mahjong Tile Efficiency

  • Calculate shanten number of mahjong hands.
  • Support multiple rulesets (Menzu, Hong Kong Old Style, Riichi, ZungJung, MCR, Taiwan, Hong Kong Taiwan Style)
  • Calculate ukeire (tile acceptace)

API

TilesToHand

Convert a hand of tiles format to hand format

const tiles = [
  '1m', '2m', '3m', '6p', '7p', '7p', '7p', '8p', '8p', '5s', '5s', '1z', '1z'
]
const hand = tilesToHand(tiles)
console.log(hand)
// [
//   [1, 1, 1, 0, 0, 0, 0, 0, 0],
//   [0, 0, 0, 0, 0, 1, 3, 2, 0],
//   [0, 0, 0, 0, 2, 0, 0, 0, 0],
//   [2, 0, 0, 0, 0, 0, 0]
// ]

RuleSet

A RuleSet is a class. An instance of RuleSet has two functions: calShanten and calUkeire. Both functions take in a hand as param.

import { tilesToHand, RuleSet } from 'mahjong-tile-efficiency'
const tiles = [
  '1m', '2m', '3m', '6p', '7p', '7p', '7p', '8p', '8p', '5s', '5s', '1z', '1z'
]
const hand = tilesToHand(tiles)

const riichiRule = new RuleSet('Riichi')  // 'Menzu' | 'HK' | 'Riichi' | 'ZungJung' | 'MCR' | 'Taiwan' | 'HKTW'
const shantenResult = riichiRule.calShanten(hand)
const ukeireResult = riichiRule.calUkeire(hand)

console.log(shantenResult)
console.log(ukeireResult)

// 1
// {
//   shanten: 1,
//   ukeire: { '6p': 3, '7p': 1, '8p': 2, '9p': 4, '5s': 2, '1z': 2 },
//   totalUkeire: 14
// }

Note: if is a karaten (empty tenpai, waiting for the "fifth tile"), the function still count this as tenpai (returns 0).

calShanten function works on either (3n + 1) or (3n + 2) tiles.

calUkeire function also works on either (3n + 1) or (3n + 2) tiles, but behavior are different

  • With 3n + 1 tiles, the status is "to draw". calUkeire().ukeire tells what next drawn tiles can advance the shanten number, and the number of such tiles that are unseen.
  • With 3n + 2 tiles, the status is "to discard". calUkeire().normalDiscard tells what discard can keep the shanten number, while calUkeire().recedingDiscard tells what discard will make shaten number increases (usually inferior play).
import { tilesToHand, RuleSet } from 'mahjong-tile-efficiency'
const tiles = [
  '1m', '1m', '1m', '6p', '7p', '7p', '1s', '1s', '2s', '5s', '5s', '1z', '1z', '1z'
]
const hand = tilesToHand(tiles)

const riichiRule = new RuleSet('Riichi')
const ukeireResult = riichiRule.calUkeire(hand)

console.log(ukeireResult)
// {
//   shanten: 1,
//   normalDiscard: {
//     '1m': { '6p': 3, '2s': 3 },
//     '6p': { '7p': 2, '1s': 2, '3s': 4, '5s': 2 },
//     '7p': { '5p': 4, '8p': 4, '1s': 2, '3s': 4, '5s': 2 },
//     '1s': { '5p': 4, '7p': 2, '8p': 4, '3s': 4, '5s': 2 },
//     '2s': { '5p': 4, '7p': 2, '8p': 4, '1s': 2, '5s': 2 },
//     '1z': { '6p': 3, '2s': 3 }
//   },
//   recedingDiscard: {
//     '5s': {
//       '4p': 4,
//       '5p': 4,
//       '6p': 3,
//       '7p': 2,
//       '8p': 4,
//       '9p': 4,
//       '1s': 2,
//       '2s': 3,
//       '3s': 4,
//       '4s': 4,
//       '5s': 3,
//       '6s': 4,
//       '7s': 4
//     }
//   }

Calculate shanten based on final shape

Each mahjong rule consists of different winning pattern.

  • calShantenMenzu: 面子手 standard hand
  • calShantenChiitoi: 七對子 7 pairs (disallow identical pairs)
  • calShantenSevenPairs: 七對 7 pairs (allow identical pairs)
  • calShantenKokushi: 十三么九 / 十三么 / 國士無雙 13 orphans.
  • calShantenHonourAndKnittedTiles: 全不靠 (see MCR rules)
  • calShantenKnittedStraight: 組合龍 (see MCR rules)
  • calShantenLikgu: 嚦咕嚦咕 (see HKTW rules)
  • calShantenBatDaap: 十六不搭 (see HKTW rules)
  • calShantenSapSaamJiu: 十三么 (specifically for HKTW rules)

You can calculate the shanten specifically for a winning pattern. For example:

import { cal, tilesToHand } from 'mahjong-tile-efficiency'


const tiles = [
  '1m', '4m', '9m', '5p', '8p', '8p', '4s', '6s', '9s', '1z', '2z', '3z', '4z', '5z'
]

const hand = tilesToHand(tiles)
console.log(cal.calShantenHonourAndKnittedTiles(hand))
// 2

Terminologies

TileName

There are 34 valid tile names, which are 1m to 9m, 1p to 9p, 1s to 9s, and 1z to 9z. m p s corresponds to "Man", "Pin", and "Sou" plain suits (萬筒索). z represents honour tiles (東南西北白發中).

The program does not support 0m 0p 0s for Aka-dora as in Riichi Mahjong.

Tiles and Hand

Both Tiles and Hand are representations of a player's hand. Tiles is an array of tiles. Hand is an array of arrays of tile count, in which each subarray represents a suit.

The following tiles and hand represents the same player's hand.

const tiles = [
  '1m', '2m', '3m', '6p', '7p', '7p', '7p', '8p', '8p', '5s', '5s', '1z', '1z'
]

const hand = [
  [1, 1, 1, 0, 0, 0, 0, 0, 0],  // man
  [0, 0, 0, 0, 0, 1, 3, 2, 0],  // pin
  [0, 0, 0, 0, 2, 0, 0, 0, 0],  // sou
  [2, 0, 0, 0, 0, 0, 0]  // zi
]

RuleName

The program supports multiple rules. Use the following literals for the rules:

  • Menzu: Standard shapes only
  • HK: Hong Kong Old Style
  • Riichi: Japanese mahjong
  • ZungJung: Zung Jung Rules (Similar to Riichi, except identical pairs are allowed for 7 pairs)
  • MCR: Chinese MCR rule
  • Taiwan: Taiwanese Rule (like menzu, but maximum 17 tiles)
  • HKTW: Taiwan Mahjong Hong Kong style (with 嚦咕嚦咕、十六不搭、十三么)