From: Ramakrishnan Muthukrishnan Date: Thu, 25 Nov 2010 18:10:08 +0000 (+0530) Subject: solution to 2.59 and 2.60 X-Git-Url: https://git.rkrishnan.org/%5B/%5D%20/uri/%22doc.html/-?a=commitdiff_plain;h=a8b4dccc26e257135dbbe73b74be799491896488;p=sicp.git solution to 2.59 and 2.60 --- diff --git a/src/sicp/ex2_59.rkt b/src/sicp/ex2_59.rkt new file mode 100644 index 0000000..b00b1b3 --- /dev/null +++ b/src/sicp/ex2_59.rkt @@ -0,0 +1,13 @@ +#lang racket + +(require "ch2_3_3.rkt") + +(define (union-set set1 set2) + (cond ((null? set1) set2) + ((null? set2) set1) + ((element-of-set? (car set1) set2) (union-set (cdr set1) set2)) + (else (cons (car set1) (union-set (cdr set1) set2))))) + + (union-set '(1 2 3 4) '(5 6 7 8)) + (union-set '(1 2 3 4) '(1 2 3 4)) + (union-set '(1 2 3 4) '(1 2 7 8)) \ No newline at end of file diff --git a/src/sicp/ex2_60.rkt b/src/sicp/ex2_60.rkt new file mode 100644 index 0000000..ea9b304 --- /dev/null +++ b/src/sicp/ex2_60.rkt @@ -0,0 +1,30 @@ +#lang racket + +(define (element-of-set? x set) + (cond ((null? set) #f) + ((equal? x (car set)) #t) + (else (element-of-set? x (cdr set))))) + +(define (adjoin-set x set) + (cons x set)) + +(define (union-set set1 set2) + (append set1 set2)) + +(define (intersection-set set1 set2) + (cond ((or (null? set1) (null set2)) '()) + ((element-of-set? (car set1) set2) (cons (car set1) (intersection-set (cdr set1) set2))) + (else (intersection-set (cdr set1) set2)))) + +#| + union-set and adjoin-set has changed. Rest remain unchanged. + + Performance while adding a new element is O(1). Same with union. + intersection-set remains the same - O(m * n). + element-of-set? also remains the same - O (n). + +If duplicates are allowed, then Intersection and element-of-set? performance will degrade. + +|# + + \ No newline at end of file