y-wing
level 5 - expertalso known as
xy-wing, bent triple
what it means
Three cells form a Y shape. One cell (pivot) connects to two others (branches). This forces a number to be eliminated elsewhere.
the y pattern
The pivot cell has two candidates. It sees two branch cells that each share one of those candidates.
the y shape
The pivot sees both branches. Together they form a Y.
how it works
- • the pivot has two numbers: A and B
- • branch 1 shares A and has C
- • branch 2 shares B and has C
- • both branches have C
- • where branches see each other, C is eliminated
analogy
game of telephone — person A tells B OR C, and that forces something elsewhere.
if the pivot is 1, then branch 1 must be 3.
if the pivot is 2, then branch 2 must be 3.
either way, a 3 appears at one of the branches.
the elimination
Both branches can see the target cell. Since one branch must be 3, the target cannot be 3.
in short
the y-wing creates a chain reaction. the pivot forces one branch to be a certain value, which eliminates that value from cells both branches can see.
this is an advanced technique. if it feels confusing, that is normal. master the basics first, then come back to y-wings.