▁in ▁group ▁theory . ▁Chapter ▁six ▁looks ▁at ▁combin atorial ▁search ▁techniques ▁for ▁finding ▁small ▁systems ▁of ▁giv ens ▁that ▁uniqu ely ▁define ▁a ▁puzz le ▁solution ; ▁soon ▁after ▁the ▁book ' s ▁publication , ▁these ▁methods ▁were ▁used ▁to ▁show ▁that ▁the ▁minimum ▁possible ▁number ▁of ▁giv ens ▁is ▁ 1 7 . ▁ ▁The ▁next ▁two ▁chap ters ▁look ▁at ▁two ▁different ▁mathematical ▁formal izations ▁of ▁the ▁problem ▁of ▁going ▁from ▁a ▁Sud oku ▁problem ▁to ▁its ▁solution , ▁one ▁involving ▁graph ▁color ing ▁( more ▁precisely , ▁pre color ing ▁extension ▁of ▁the ▁Sud oku ▁graph ) ▁and ▁another ▁involving ▁using ▁the ▁Gr ö b ner ▁basis ▁method ▁to ▁solve ▁systems ▁of ▁polynomial ▁equations . ▁The ▁final ▁chapter ▁studies ▁questions ▁in ▁extrem al ▁combin ator ics ▁motiv ated ▁by ▁Sud oku , ▁and ▁( although ▁ 7 6 ▁Sud oku ▁puzz les ▁of ▁various ▁types ▁are ▁scattered ▁throughout ▁the ▁earlier ▁chap ters ) ▁the ▁ep ilog ue ▁presents ▁a ▁collection ▁of ▁ 2 0 ▁additional ▁puzz les , ▁in ▁advanced ▁variations ▁of ▁Sud oku . ▁ ▁A udi ence ▁and ▁reception ▁This ▁book ▁is ▁intended ▁for ▁a ▁general ▁audience ▁interested ▁in ▁recre ational ▁mathematics , ▁including ▁mathemat ically ▁incl ined ▁high ▁school ▁students . ▁It ▁is ▁intended ▁to ▁counter ▁the ▁w ides p read ▁mis im pression ▁that ▁Sud oku ▁is ▁not ▁mathematical , ▁and ▁could ▁help ▁students ▁appreciate ▁the ▁distinction ▁between ▁mathematical ▁reasoning ▁and ▁ro te ▁calculation . ▁Rev iewer ▁Mark ▁Hun ace k ▁writes ▁that ▁" a