HodokuRevisited

Techniques / Subsets

Hidden Pair, Triple and Quad

Medium

N digits that can only go into the same N cells of a unit.

If two digits, say 4 and 6, appear as candidates in only two cells of a unit, then those cells must hold 4 and 6. Remove every other candidate from those two cells. That is a Hidden Pair.

Hidden subsets are the mirror image of naked subsets: a hidden pair in a unit corresponds to a naked set formed by the remaining cells. Triples and quads work the same way with three or four digits.

Notation

Hidden Pair: 2 can be removed from r1c4.

13571238257236823846919648348193872525957122457246271638295614387346782352912498141342379524673482924812812684569145141248924756282473524862347923481237812892479149
Hidden Pair: 2 can be removed from r1c4.

pattern removed

Open in app
615794237987824151353926191462493617812751456783941671672129426791278165673563267126712712675849193169815674215612425612461259123563915687825727425169163
Hidden Triple: 1 can be removed from r2c9.

pattern removed

Open in app