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qzchenwl/FindTriangles.hs

Last active August 29, 2015 14:25
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FindTriangles.hs
module Main where
import Data.List
vertices = "ABCDEFGHIJK"
edges = ["ADB", "AEC", "AFHJ", "AGIK", "BJKC", "BHIE", "DFGE"]
combinations n = filter ((==n) . length) . subsequences
inSameEdge xs = or [ all (`elem` edge) xs | edge <- edges]
isTriangle (a:b:c:[]) = all inSameEdge [[a, b], [a, c], [b, c]] && not (inSameEdge [a, b, c])
triangles = filter isTriangle (combinations 3 vertices)
main = print triangles
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["ABC","ABE","BCE","ADE","BDE","ADF","AEF","ADG","AEG","AFG","ABH","AEH","EFH","ABI","AEI","EGI","AHI","ABJ","ACJ","BHJ","ABK","ACK","BIK","AJK"]

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