Launi huɗu sun isa ga kowace taswira, ta yadda maƙwabta koyaushe suke da launi daban. An tabbatar da hakan a 1976. Amma ta yaya za a samo launukan a zahiri?
Kayan aikin gargajiya shi ne sarƙar Kempe (Kempe chain). Zaɓi launi biyu. Ka ɗauki dukan dunƙulen ƙasashe masu haɗe da juna, masu waɗannan launuka biyu kawai. Musanya su a duk faɗin dunƙulen: taswirar tana nan da launuka daidai.
Matsalar: musanya ɗaya zai iya yaɗuwa a faɗin taswirar gaba ɗaya. Tarihin baya yana buƙatar ƙarin musanya yayin da taswirori suka girma. Kowanne yana biyan cikakken zagaye kan taswirar.
Masana lissafi shida, daga Tokyo zuwa Copenhagen, sun kawar da wannan ƙarin tsada. Algorithm ɗinsu yana yi wa ƙasashe n launi cikin lokacin da ya yi daidai da n. Ana warware ƙananan sassan taswirar sau ɗaya, a ajiye su a cikin teburori, sannan a duba su kawai. Marubutan suna kiran wannan sauri mafi kyau da zai yiwu.
Tushe: Four-Coloring Planar Graphs in Linear Time, https://arxiv.org/abs/2610.39753










