Key takeaways

  • Three consecutive tiles are normally a complete chow but can reassign inside a larger hand.
  • Four-tile runs preserve both end extensions or split into neighboring blocks.
  • Five-tile runs offer more meld-block exchanges but are not two completed melds.
  • Shared tiles can form useful compound flexibility and should not be broken automatically.
  • The right decomposition depends on whether the whole hand needs melds, a pair, blocks, or safety.

Why can local shapes not be fixed?

The shape 345m looks like a completed chow. The shape 3456m is often labeled 345 + 6. But if the hand already has enough melds and needs two blocks, 34 + 56 can be more useful.

Roles depend on:

  • Completed meld count
  • Whether a pair exists
  • Remaining block demand
  • Effective tiles in other suits
  • Current shanten and rules objective

Decomposition optimizes the whole hand; it does not assign one permanent label to each local group.

Reading a three-tile run

The shape 345m is a complete chow but can change after new tiles:

  • Draw 2m to create 2345.
  • Draw 6m to create 3456.
  • Add another 3m, 4m, or 5m to create pair and sequence choices.

Completed melds are normally stable, but larger compounds, insufficient blocks, or a route switch can justify reconsidering them.

Three roles for a four-tile run

For 3456m:

  1. 345 + 6: a complete meld and central floater.
  2. 3 + 456: another complete meld and floater.
  3. 34 + 56: two two-sided blocks whose overlap and capacity must be checked.

Its strength is extension on both ends. Draws such as 2m or 7m can lengthen the connected region; duplicate draws can provide a pair or pung route.

What changes with five tiles?

The shape 34567p can support:

  • 345 + 67
  • 34 + 567
  • 456 + 3 + 7
  • Larger compounds with other same-suit tiles

Five physical tiles cannot already make two three-tile melds. Their value is the ability to choose which three become a meld after a draw and what role the other two take.

Is sharing overlap or flexibility?

Useful sharing

  • Many draws permit a new meld-block assignment.
  • Breaking one tile substantially shrinks the effective set.
  • Improvements often reach two-sided or multi-sided shapes.
  • The hand has enough remaining meld slots to use the development.

Harmful overlap

  • Candidates exceed remaining meld capacity.
  • Headline acceptance depends heavily on the same tile.
  • Breaking one side preserves shanten and clarifies roles.
  • One tile is counted in two completed units.

Judge overlap by what happens to the whole hand after breaking, not by sharing alone.

What about gapped compounds?

The shape 246m contains the inside blocks 24 and 46. They accept different direct tiles and can share improvements. List:

  1. Direct shanten-reducing draws
  2. Same-shanten draws that create two-sided shape
  3. The tile that becomes redundant after each draw
  4. Overlap with other blocks

Do not add two local inside-block totals without building the hand-wide union.

Why are tiles beside a concealed pung special?

The shape 555m plus 4m and 6m can remain a pung with neighbors or be decomposed into 345 and 456 routes after future draws.

The trap is reusing 5m. You cannot retain all three copies as a completed pung while using two of those same copies in two sequences. Allocate every physical tile in each decomposition and verify the count.

Six steps for a long shape

  1. Select a four-meld 13-tile or five-meld 16-tile target.
  2. Identify fixed melds and the pair in the whole hand.
  3. List every legal decomposition of the connected shape.
  4. Build the effective-tile union and subtract visible copies.
  5. Reassign meld and block roles after major draws.
  6. Compare shanten, second-order ukeire, rules value, and game state.

When should connected shape usually stay?

  • The hand is two-shanten or farther and needs development.
  • Central tiles have live internal and end extensions.
  • Other blocks are narrow or restricted by kabe.
  • The pair is not fixed and duplicate draws can supply it.
  • Removing one tile destroys several routes at once.

When can it be broken?

  • The hand is at tenpai or one-shanten and needs a fixed widest current route.
  • Meld candidates severely exceed capacity.
  • Key extension tiles are heavily visible.
  • Yaku, fan, tai, or safety gives a clear rules-based reason.

Common mistakes

  • Always treating four tiles as a chow plus floater.
  • Counting five tiles as two completed melds.
  • Assigning one tile to two melds.
  • Adding local acceptance without a hand-wide union.
  • Treating every shared tile as harmful overlap.
  • Preserving an attractive run while ignoring shanten and visible tiles.

Scope and limitations

This article covers standard-hand decomposition. Seven Pairs, flush routes, and 16-tile capacity change tile roles. The examples demonstrate structure and do not supply a unique discard outside a complete hand.

Practicing legal decomposition with Tingpai Lab

Write every decomposition as non-overlapping melds, blocks, and floaters before counting candidates. When checking the explanation, identify the second-order routes preserved by the answer instead of memorizing “four-tile runs are strong” as another slogan.

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