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authorDavid Thompson <dthompson2@worcester.edu>2014-02-02 18:10:02 -0500
committerDavid Thompson <dthompson2@worcester.edu>2014-02-02 18:10:02 -0500
commit22a668de0d4487543db6de8c738dd132dc591fe5 (patch)
tree721d1acc57f213441cb2641593d903d2cc51f355 /problem-8.scm
parent1a350525867996f57ebb5d7c428ba8929d4995c6 (diff)
Solve problem 8.
Diffstat (limited to 'problem-8.scm')
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1 files changed, 21 insertions, 0 deletions
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+(use-modules (srfi srfi-1)
+ (srfi srfi-42))
+
+(define big-ass-number
+ "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450")
+
+(define (digit str i)
+ (string->number (substring str i (1+ i))))
+
+(define (five-digits numstring start)
+ (list (digit numstring start)
+ (digit numstring (+ start 1))
+ (digit numstring (+ start 2))
+ (digit numstring (+ start 3))
+ (digit numstring (+ start 4))))
+
+(define (five-digit-products numstring)
+ (list-ec (: i (- (string-length numstring) 6))
+ (apply * (five-digits numstring i))))
+
+(reduce max 0 (five-digit-products big-ass-number))