Iishanten: Difference between revisions

26 bytes removed ,  2 October 2023
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→‎Main four types: all of the rests can be used as individual word so left as-is.
(Additional descriptions of all iishanten types.)
m (→‎Main four types: all of the rests can be used as individual word so left as-is.)
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'''Iishanten''' is the state of the hand, where one tile is needed to achieve [[tenpai]].  This is the [[Shanten|closest state of a hand]] to tenpai.
'''Iishanten''' is the state of the hand, where one tile is needed to achieve [[tenpai]].  This is the [[Shanten|closest state of a hand]] to tenpai.


==Main four types==
== Main four types ==
The four types are based on the possible configurations regarding complete and incomplete [[tile groups]].
The four types are based on the possible configurations regarding complete and incomplete [[tile groups]].


===Yojouhai iishanen===
=== Yojouhai ===
{{#mjt:234m4578s22567p1z}}
{{#mjt:234m4578s22567p1z}}


'''Floating tile''' '''iishanten''' describes the case where there are two complete groups and a pair, with two incomplete groups waiting to be completed. One tile (the East tile in the example hand) does not contribute to any group, and so is said to be floating.
'''Floating tile''' '''iishanten''' describes the case where there are two complete groups and a pair, with two incomplete groups waiting to be completed. One tile (the East tile in the example hand) does not contribute to any group, and so is said to be floating.


===Kanzen iishanten===
=== Kanzenke ===
{{#mjt:234m44578s22567p}}
{{#mjt:234m44578s22567p}}


'''Complete iishanten''' is an improvement on floating iishanten when all tiles in the hand contribute to the iishanten. In the example hand, the 445s group now has three tiles working together. This hand is also an example of '''perfect iishanten'''. Perfect iishanten is a special type of complete iishanten that guarantees a ryanmen wait. If we draw 369s2p, we can discard 4s for a multisided wait. If we draw 4s, we discard 5s.
'''Complete iishanten''' is an improvement on floating iishanten when all tiles in the hand contribute to the iishanten. In the example hand, the 445s group now has three tiles working together. This hand is also an example of '''perfect iishanten'''. Perfect iishanten is a special type of complete iishanten that guarantees a ryanmen wait. If we draw 369s2p, we can discard 4s for a multisided wait. If we draw 4s, we discard 5s.


===Atamanai iishanten===
=== Atamanai ===
{{#mjt:123m456789p2378s}}
{{#mjt:123m456789p2378s}}


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With an ankou in the hand, the above shape becomes even more advantageous.  The completion of either of the ryanmen can bring about pinfu by discarding one tile from the ankou and use the remaining two as the pair.
With an ankou in the hand, the above shape becomes even more advantageous.  The completion of either of the ryanmen can bring about pinfu by discarding one tile from the ankou and use the remaining two as the pair.


===Kuttsuki iishanten===
=== Kuttsuki ===
{{#mjt:234678m37s22567p}}
{{#mjt:234678m37s22567p}}


'''Sticky iishanten''' is identified by three complete groups, one pair, and two floating tiles (37s in the example above). This type of iishanten tends to have the largest range of acceptable tiles to bring it to tenpai (any souzu tile in the example). However, the downside is that many of these draws may leave a narrow, non-ryanmen wait.
'''Sticky iishanten''' is identified by three complete groups, one pair, and two floating tiles (37s in the example above). This type of iishanten tends to have the largest range of acceptable tiles to bring it to tenpai (any souzu tile in the example). However, the downside is that many of these draws may leave a narrow, non-ryanmen wait.
== Chiitoitsu ==
== Chiitoitsu ==
{{main|Chiitoitsu}}
{{main|Chiitoitsu}}