X-Git-Url: https://git.rkrishnan.org/?p=sicp.git;a=blobdiff_plain;f=src%2Fsicp%2Fdistinct.rkt;fp=src%2Fsicp%2Fdistinct.rkt;h=3f2e2e0b7f1c31a600aba96eedcb8d8788d0f09f;hp=0000000000000000000000000000000000000000;hb=50cef372de91c41185de4fac8a1fc456c978b28a;hpb=07f6c2a14b01e1a1f9c585c8a53086fbb819f8f8

diff --git a/src/sicp/distinct.rkt b/src/sicp/distinct.rkt
new file mode 100644
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+++ b/src/sicp/distinct.rkt
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+#lang racket
+
+(provide distinct?)
+
+(define (distinct? xs)
+  (let loop [(s (set))
+             (r xs)]
+    (cond [(empty? r) #t]
+          [(set-member? s (first r)) #f]
+          [else (loop (set-add s (first r)) (rest r))])))
+
+(module+ test
+  (require rackunit)
+  
+  (check-equal? (distinct? '()) #t)
+  (check-equal? (distinct? '(1)) #t)
+  (check-equal? (distinct? '(1 2)) #t)
+  (check-equal? (distinct? '(1 1)) #f)
+  (check-equal? (distinct? '(1 2 3)) #t)
+  (check-equal? (distinct? '(1 2 3 3 2)) #f)
+  (check-equal? (distinct? '(a b)) #t)
+  (check-equal? (distinct? '(a b a)) #f)
+  (check-equal? (distinct? '(a b c c)) #f)
+  (check-equal? (distinct? '(1 2 3 4)) #t)
+  (check-equal? (distinct? '(1 2 3 4 5)) #t)
+  (check-equal? (distinct? '(1 (2 3) 4 2 3)) #t))
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