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euler011.lisp
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euler011.lisp
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;;;;
;;;; Project Euler - Problem 11
;;;;
(setf *suppress-similar-constant-redefinition-warning* t)
(defconstant *euler011-array*
(make-array '(20 20) :initial-contents
'((08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08)
(49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00)
(81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65)
(52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91)
(22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80)
(24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50)
(32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70)
(67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21)
(24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72)
(21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95)
(78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92)
(16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57)
(86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58)
(19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40)
(04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66)
(88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69)
(04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36)
(20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16)
(20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54)
(01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48))))
(defun euler011 ()
(let ((greatest-product 0))
(dotimes (x 20)
(dotimes (y 20)
(if (> (product+x x y) greatest-product)
(setf greatest-product (product+x x y)))
(if (> (product+x+y x y) greatest-product)
(setf greatest-product (product+x+y x y)))
(if (> (product+y x y) greatest-product)
(setf greatest-product (product+y x y)))
(if (> (product-x+y x y) greatest-product)
(setf greatest-product (product-x+y x y)))
))
greatest-product))
(defun product+x (x y)
(if (> x 16)
0
(* (aref *euler011-array* y x)
(aref *euler011-array* y (+ 1 x))
(aref *euler011-array* y (+ 2 x))
(aref *euler011-array* y (+ 3 x)))))
(defun product+x+y (x y)
(if (or (> x 16) (> y 16))
0
(* (aref *euler011-array* y x)
(aref *euler011-array* (+ 1 y) (+ 1 x))
(aref *euler011-array* (+ 2 y) (+ 2 x))
(aref *euler011-array* (+ 3 y) (+ 3 x)))))
(defun product+y (x y)
(if (> y 16)
0
(* (aref *euler011-array* y x)
(aref *euler011-array* (+ 1 y) x)
(aref *euler011-array* (+ 2 y) x)
(aref *euler011-array* (+ 3 y) x))))
(defun product-x+y (x y)
(if (or (< x 3) (> y 16))
0
(* (aref *euler011-array* y x)
(aref *euler011-array* (+ y 1) (- x 1))
(aref *euler011-array* (+ y 2) (- x 2))
(aref *euler011-array* (+ y 3) (- x 3)))))