--- a/euler.asd Mon Feb 13 13:32:08 2017 +0000
+++ b/euler.asd Mon Feb 13 18:58:19 2017 +0000
@@ -10,13 +10,9 @@
:depends-on (
- :fare-quasiquote-optima
- :fare-quasiquote-readtable
:fiveam
:iterate
:losh
- :optima
- :trivial-types
)
--- a/src/euler.lisp Mon Feb 13 13:32:08 2017 +0000
+++ b/src/euler.lisp Mon Feb 13 18:58:19 2017 +0000
@@ -475,6 +475,44 @@
(sum (range 1 (1+ 1000))
:key #'silly-british-letters)))
+(defun problem-18 ()
+ ;; By starting at the top of the triangle below and moving to adjacent numbers
+ ;; on the row below, the maximum total from top to bottom is 23.
+ ;;
+ ;; 3
+ ;; 7 4
+ ;; 2 4 6
+ ;; 8 5 9 3
+ ;;
+ ;; That is, 3 + 7 + 4 + 9 = 23.
+ ;;
+ ;; Find the maximum total from top to bottom of the triangle below.
+ ;;
+ ;; NOTE: As there are only 16384 routes, it is possible to solve this problem
+ ;; by trying every route. However, Problem 67, is the same challenge with
+ ;; a triangle containing one-hundred rows; it cannot be solved by brute force,
+ ;; and requires a clever method! ;o)
+ (let ((triangle '((75)
+ (95 64)
+ (17 47 82)
+ (18 35 87 10)
+ (20 04 82 47 65)
+ (19 01 23 75 03 34)
+ (88 02 77 73 07 63 67)
+ (99 65 04 28 06 16 70 92)
+ (41 41 26 56 83 40 80 70 33)
+ (41 48 72 33 47 32 37 16 94 29)
+ (53 71 44 65 25 43 91 52 97 51 14)
+ (70 11 33 28 77 73 17 78 39 68 17 57)
+ (91 71 52 38 17 14 91 43 58 50 27 29 48)
+ (63 66 04 68 89 53 67 30 73 16 69 87 40 31)
+ (04 62 98 27 23 09 70 98 73 93 38 53 60 04 23))))
+ (car (reduce (lambda (last next)
+ (mapcar #'+
+ (mapcar #'max last (rest last))
+ next))
+ (reverse triangle)))))
+
;;;; Tests --------------------------------------------------------------------
(def-suite :euler)
@@ -497,6 +535,7 @@
(test p15 (is (= 137846528820 (problem-15))))
(test p16 (is (= 1366 (problem-16))))
(test p17 (is (= 21124 (problem-17))))
+(test p18 (is (= 1074 (problem-18))))
;; (run! :euler)