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Shanten (view source)

Revision as of 17:41, 6 January 2025

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Multiple methods can be used to count a hand's shanten. These can be used to get a quick estimate of shanten during a game.
Multiple methods can be used to count a hand's shanten. These can be used to get a quick estimate of shanten during a game.


Blocks are defined as taatsu, pairs, and tile groups.
Note that blocks are defined as taatsu, pairs, and tile groups.


=== "Useless" tile estimate ===
=== "Useless" tile estimate ===
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*Every hand starts at 8-shanten.
*Every hand starts at 8-shanten.
*Each complete group reduces shanten by 2. Each taatsu/pair in hand reduces shanten by 1.  
*Each complete group reduces shanten by 2. Each taatsu/pair in hand reduces shanten by 1.  
**However, once a hand has 4 blocks, any blocks past the 4th no longer count towards this. This is because mahjong hands require exactly 4 tile groups.
**However, once a hand has 4 blocks, any blocks past the 4th no longer count. This is because mahjong hands require exactly 4 tile groups.
*When the hand has one pair (''in addition to 4 other blocks''), shanten is reduced by 1
*When the hand has one pair (''in addition to 4 other blocks''), shanten is reduced by a further 1.


For example, a hand with 6 taatsu and a lone tile is not (8-6=) 2-shanten; it is instead (8-4=) 4-shanten. A hand with 5 taatsu + 1 pair would be (8-4-1=) 3-shanten.
For example, a hand with 6 taatsu and a lone tile is not (8-6=) 2-shanten; it is instead (8-4=) 4-shanten. A hand with 5 taatsu + 1 pair would be (8-4-1=) 3-shanten.
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** If a hand has 4 groups + 0 pairs: Set to tenpai
** If a hand has 4 groups + 0 pairs: Set to tenpai


For "blocks" = (taatsu/pairs/groups). This is identical to the above calculation, but assumes all hands have a pair, then adds +1 shanten if it doesn't actually have a pair. This generalization works in most cases; notable exceptions include hands with 3 groups + 1 taatsu + 2 isolated tiles (which is 1-shanten), or 4 groups + 1 lone tile (which is tenpai).
This is identical to the above calculation, but assumes all hands have a pair, then adds +1 shanten if it doesn't actually have a pair. This generalization works in most cases; notable exceptions include hands with 3 groups + 1 taatsu + 2 isolated tiles (which is 1-shanten), or 4 groups + 1 lone tile (which is tenpai).


=== Chiitoitsu ===
=== Chiitoitsu ===
Hordes
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edits

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