Iishanten: Difference between revisions

Revision as of 22:24, 24 July 2024

Iishanten is the state of a hand where one tile is needed to achieve tenpai. This is the closest state to tenpai.

Four main types

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

Yojouhai

Waiting for: (to form a sequence)

Floating tile iishanten 「余剰牌」 is a hand with 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.

Kanzenkei

Waiting for: (to form a sequence), (to form a triplet)

Complete iishanten 「完全形、完全イーシャンテン」 is an improvement on floating iishanten where all tiles in the hand contribute to the iishanten. In the example hand, the 223s group now has three tiles working together.

This hand is also an example of perfect iishanten. Perfect iishanten is a complete iishanten with two ryanmen groups, thus guaranteeing a ryanmen wait.

Atamanashi

Waiting for: (to form a sequence), (to form a pair)

Headless iishanten 「頭なし、ヘッドレス」 is a hand with three complete groups, no pair, and one/two incomplete groups. An ideal headless hand, as shown above, will have two ryanmen groups waiting to be completed. If either ryanmen is completed, the hand enters tenpai with a tanki wait. If any of the four tiles are paired, the other tile of its group can be discarded, forming a wait with the other ryanmen. (E.g. if a 2s is drawn, discard 3s to enter a ryanmen tenpai.)

With a triplet

Waiting for: (to form a sequence), (to form a pair)

Headless iishanten + closed triplet is a stronger version of headless iishanten. Here, if either ryanmen is completed, then the triplet can be discarded (turning it into a pair), thus retaining a ryanmen wait.

Assuming the hand has two ryanmen groups:

A headless iishanten without a triplet has better tile acceptance than a perfect iishanten, but there are fewer tiles that lead to a ryanmen wait at tenpai.
A headless iishanten with a triplet has better acceptance than perfect iishanten, and has more tiles that end with a ryanmen wait.

Kuttsuki

Waiting for: (to form a group)

Sticky iishanten 「くっつき」 is a hand with three complete groups, one pair, and two floating tiles. This type of iishanten tends to accept the most tiles, but many of those tiles lead to a non-ryanmen wait.

Chiitoitsu

Main article: Chiitoitsu

Waiting for: (to form a pair)

A hand is iishanten for chiitoitsu when the hand has five pairs. This leaves three individual tiles waiting to be paired.

If one of the tiles is part of a triplet, it becomes easier to convert the hand to toitoi, but only two tiles can be paired.

Kokushi musou

Main article: Kokushi musou

11 unique tiles, 1 pair Waiting for: (to enter a 1-sided wait)

12 unique tiles Waiting for: (to enter a 13-sided wait), (to enter a 1-sided wait)

External links

一向聴

Iishanten in Japanese Wikipedia

【麻雀】上がりを増やす！イーシャンテンの秘密【初心者向け講座】 (YouTube)

Video covering iishanten shapes

@@ Line 1: / Line 1: @@
-'''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 a hand where one tile is needed to achieve [[tenpai]]. This is the [[Shanten|closest state]] to tenpai.
-== Main four types ==
+== Four main types ==
 The four types are based on the possible configurations regarding complete and incomplete [[tile groups]].
 === Yojouhai ===
-{{#mjt:234m2378s22567p1z}}
+{{#mjt:234m2378s22567p1z}} Waiting for: {{#mjt:1469s}} (to form a sequence)
-'''Floating tile iishanten''' {{kana|余剰牌}} 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''' {{kana|余剰牌}} is a hand with 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.
 === Kanzenkei ===
-{{#mjt:234m22378s22567p}}
+{{#mjt:234m22378s22567p}} Waiting for: {{#mjt:1469s}} (to form a sequence), {{#mjt:2s2p}} (to form a triplet)
-'''Complete iishanten''' {{kana|完全形、完全イーシャンテン}} is an improvement on floating iishanten when all tiles in the hand contribute to the iishanten. In the example hand, the 223s 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 1469s, we can discard 2s for a ryanmen wait. If we draw 2s or 2p, we discard 3s to wait on 69s to complete the 78s group.
+'''Complete iishanten''' {{kana|完全形、完全イーシャンテン}} is an improvement on floating iishanten where all tiles in the hand contribute to the iishanten. In the example hand, the 223s group now has three tiles working together.
+This hand is also an example of '''perfect iishanten'''. Perfect iishanten is a complete iishanten with two ryanmen groups, thus guaranteeing a ryanmen wait.
 === Atamanashi ===
-{{#mjt:123m2378s456789p}}
+{{#mjt:123m2378s456789p}} Waiting for: {{#mjt:1469s}} (to form a sequence), {{#mjt:2367s}} (to form a pair)
+'''Headless iishanten''' {{kana|頭なし、ヘッドレス}} is a hand with three complete groups, no pair, and one/two incomplete groups. An ideal headless hand, as shown above, will have two ryanmen groups waiting to be completed. If either ryanmen is completed, the hand enters tenpai with a tanki wait. If any of the four tiles are paired, the other tile of its group can be discarded, forming a wait with the other ryanmen. (E.g. if a 2s is drawn, discard 3s to enter a ryanmen tenpai.)
+'''With a triplet'''
-'''Headless iishanten''' {{kana|頭なし、ヘッドレス}} is a hand where we have three complete groups, no pair, and one or two incomplete groups. An ideal headless hand will have two ryanmen groups waiting to be completed. If either of these groups completes, then the hand becomes tenpai with a tanki wait. If we pair one of the four tiles, then we can discard the other tile in its incomplete group to get a ryanmen wait on the other incomplete group.
+{{#mjt:123m2378s222789p}} Waiting for: {{#mjt:1469s}} (to form a sequence), {{#mjt:2367s}} (to form a pair)
-{{#mjt:123m2378s222789p}}
+'''Headless iishanten + closed triplet''' is a stronger version of headless iishanten. Here, if either ryanmen is completed, then the triplet can be discarded (turning it into a pair), thus retaining a ryanmen wait.
-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.
+Assuming the hand has two ryanmen groups:
+* A headless iishanten without a triplet has better tile acceptance than a perfect iishanten, but there are fewer tiles that lead to a ryanmen wait at tenpai.
+* A headless iishanten with a triplet has better acceptance than perfect iishanten, and has more tiles that end with a ryanmen wait.
 === Kuttsuki ===
-{{#mjt:234678m37s22567p}}
+{{#mjt:234678m37s22567p}} Waiting for: {{#mjt:123456789s}} (to form a group)
+'''Sticky iishanten''' {{kana|くっつき}} is a hand with three complete groups, one pair, and two floating tiles. This type of iishanten tends to accept the most tiles, but many of those tiles lead to a non-ryanmen wait.
-'''Sticky iishanten''' {{kana|くっつき}} 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 ==
 {{main|Chiitoitsu}}
-{{#mjt:1166m4499s667p25z}}
+{{#mjt:1166m4499s667p25z}} Waiting for: {{#mjt:7p25z}} (to form a pair)
-Chiitoitsu achieves 1-shanten, when the developing hand is at five pairs.  That potentially leaves three individual tiles waiting to be paired. At least one of the tiles could be occupied as part of a triplet, which actually reduces possible pairing tiles down to two.
+A hand is iishanten for chiitoitsu when the hand has five pairs. This leaves three individual tiles waiting to be paired.
+If one of the tiles is part of a triplet, it becomes easier to convert the hand to [[toitoi]], but only two tiles can be paired.
 == Kokushi musou ==
 {{main|Kokushi musou}}
+'''11 unique tiles, 1 pair'''
+{{#mjt: 1m139p19s1234566z}} Waiting for: {{#mjt:9m7z}} (to enter a 1-sided wait)
+'''12 unique tiles'''
+{{#mjt: 19m139p19s123456z}} Waiting for: {{#mjt:7z}} (to enter a 13-sided wait), {{#mjt: 19m19p19s123456z}} (to enter a 1-sided wait)
 ==External links==