add one/fourteen.scm

1 files changed, 29 insertions, 0 deletions

diff --git a/one/fourteen.scm b/one/fourteen.scm
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--- /dev/null
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+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+;;; source from section 1.2.2
+
+(define-module (one fourteen)
+  #:export (count-change
+            cc
+            first-denomination))
+
+(define (count-change amount)
+  (cc amount 5))
+
+(define (cc amount kinds-of-coins)
+  (cond ((= amount 0) 1)
+        ((or (< amount 0) (= kinds-of-coins 0)) 0)
+        (else (+ (cc amount
+                     (- kinds-of-coins 1))
+                 (cc (- amount
+                        (first-denomination kinds-of-coins))
+                     kinds-of-coins)))))
+
+(define (first-denomination kinds-of-coins)
+  (cond ((= kinds-of-coins 1) 1)
+        ((= kinds-of-coins 2) 5)
+        ((= kinds-of-coins 3) 10)
+        ((= kinds-of-coins 4) 25)
+        ((= kinds-of-coins 5) 50)))