Ikkitsuukan: Difference between revisions

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In this counter example, the tiles 1-9 for one suit are in the hand, but ittsuu would not be counted.  Instead, they are grouped as 123, 567, and 789, with 4-man functioning as the [[Jantou|pair]].
In this counter example, the tiles 1-9 for one suit are in the hand, but ittsuu would not be counted.  Instead, they are grouped as 123, 567, and 789, with 4-man functioning as the [[Jantou|pair]].


==Discard characteristics==
===Discard characteristics===
Hands aiming for ittsu often lack a particular suit, as a good number of one suit is collected in the hand.
Hands aiming for ittsu often lack a particular suit, as a good number of one suit is collected in the hand.


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{{Yaku compatibility table|ITT}}
{{Yaku compatibility table|ITT}}


This yaku only leaves room for one tile group of any type, such as a triplet. Therefore, any yaku that requires more than one triplet, including [[sanshoku doukou]], [[toitoi]], [[sanankou]], [[sankantsu]], and [[shousangen]], is deemed incompatible. [[Chiitoitsu]] is likewise incompatible as it does not use [[mentsu]]. [[Tanyao]], [[chanta]], [[junchan]], and [[honroutou]] are incompatible as the 456 group contains no terminals or honours, but the 123 and 789 groups contain terminals. Finally, ittsuu is incompatible with [[sanshoku doujun]] and [[ryanpeikou]] as they each require at least three sequences in a way that are incompatible with the sequences used for ittsuu.
Ittsu requires three groups to be sequences, leaving room for only one other tile group. Yaku that require more than one triplet - [[sanshoku doukou]], [[sanankou]], [[sankantsu]], [[shousangen]], [[toitoi]] - are thus incompatible. Similarly, [[sanshoku]] and [[ryanpeikou]] are incompatible because there is no room for their patterns. [[Chiitoitsu]], which does not use [[mentsu]], is likewise incompatible. The 456 sequence invalidates [[chanta]], [[junchan]], and [[honroutou]], while the 123 and 789 sequences invalidate [[tanyao]].  


=== With sanshoku ===
Ittsu can often be combined with [[honitsu]]/[[chinitsu]], as the ittsu is already composed of 9 tiles of the same suit. [[Pinfu]] also combines well; however, if the ittsu section is not complete, the hand would be subject to to [[takame and yasume]] (only one of two waiting tiles would score this yaku).
 
===Vs sanshoku===
{{main|Ittsu vs sanshoku}}
{{main|Ittsu vs sanshoku}}
Ittsuu requires three out of the four tile groups to be composed of sequences: 123, 456, and 789.  Sanshoku also requires at least three groups of sequences.  Sometimes, a hand may be 1-shanten from either yaku because of composition.  There comes a point where a player may need to choose one yaku over the other, depending on the circumstances.
Ittsuu requires three out of the four tile groups to be composed of sequences: 123, 456, and 789.  Sanshoku also requires at least three groups of sequences.  Sometimes, a hand may be 1-shanten for both yaku because of composition, forcing players to decide one or the other.
 
=== With pinfu ===
[[Pinfu]] requires a [[machi|wait pattern]] consisting of [[ryanmen]] (open wait) or a related wait like [[ryanmenten]] (three sided open). If a hand is waiting to complete the 1-9 pattern, a ryanmen wait would be subject to [[takame and yasume]]: only one tile would complete the ittsu.
 
However, this problem is completely averted if the hand already contains the full 1-9 pattern, with a wait depending on the extra tile group.


=== With honitsu and chinitsu ===
==Usage==
Ittsuu already contains nine tiles (1-9) of a single suit, so [[honitsu]] and [[chinitsu]] naturally combine with ittsuu. To form those yaku, the remaining four tiles (plus one winning tile) have to be composed of the same suit or an honor tile.
Despite being easy to memorize, ittsu is one of the more difficult yaku to obtain.


With closed hands, this combination produces some very powerful hands.  With honitsu, the hand produces [[mangan]]; while it is [[baiman]] with chinitsu.
[[Sanshoku]] is worth the same (2 han) and has a similar requirement (3 identical sequences). However, sanshoku occurs more than twice as often as ittsu. This is likely because ittsu's 123 and 789 sequences are harder to form than other sequences.


==External links==
==External links==
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