Euler problems/81 to 90
Revision as of 13:20, 24 August 2007
Find the minimal path sum from the top left to the bottom right by moving right and down.
import Data.List (unfoldr) columns s = unfoldr f s where f  = Nothing f xs = Just $ (\(a,b) -> (read a, drop 1 b)) $ break (==',') xs firstLine ls = scanl1 (+) ls nextLine pl  = pl nextLine pl (n:nl) = nextLine p' nl where p' = nextCell (head pl) pl n nextCell _   =  nextCell pc (p:pl) (n:nl) = pc' : nextCell pc' pl nl where pc' = n + min p pc minSum (p:nl) = last $ nextLine p' nl where p' = firstLine p problem_81 c = minSum $ map columns $ lines c
Find the minimal path sum from the left column to the right column.
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Find the minimal path sum from the top left to the bottom right by moving left, right, up, and down.
problem_83 = undefined
In the game, Monopoly, find the three most popular squares when using two 4-sided dice.
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Investigating the number of rectangles in a rectangular grid.
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Exploring the shortest path from one corner of a cuboid to another.
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Investigating numbers that can be expressed as the sum of a prime square, cube, and fourth power?
import List problem_87 = length expressible where limit = 50000000 squares = takeWhile (<limit) (map (^2) primes) cubes = takeWhile (<limit) (map (^3) primes) fourths = takeWhile (<limit) (map (^4) primes) choices = [[s,c,f] | s <- squares, c <- cubes, f <- fourths] unique = map head . group . sort expressible = filter (<limit) . unique . map sum $ choices
Exploring minimal product-sum numbers for sets of different sizes.
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Develop a method to express Roman numerals in minimal form.
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10 Problem 90
An unexpected way of using two cubes to make a square.
problem_90 = undefined