Aryadev Chavali
3592ea3134
Decided to try my hand at racket, fundamentally the algorithm is the same and code structure is basically the same anyway. Just looks cleaner.
25 lines
895 B
Racket
25 lines
895 B
Racket
#lang racket
|
|
|
|
(define (subsets-of lst n)
|
|
(cond
|
|
[(null? lst) null] ; 0 ways of making anything out of empty set
|
|
[(= n 0) (list null)] ; 1 way of making a 0 sized subset of something
|
|
[(= n 1) (map list lst)] ; |lst| ways of making singletons
|
|
[else
|
|
(let ([head (car lst)]
|
|
[tail (cdr lst)])
|
|
(append
|
|
;; HEAD is a part of the subset, so the rest of the subset
|
|
;; must be an n-1 sized subset of TAIL
|
|
(map (lambda (lst) (cons head lst))
|
|
(subsets-of tail (- n 1)))
|
|
;; ... or HEAD is not part of the subset, so the subset is
|
|
;; some n sized subset of TAIL
|
|
(subsets-of tail n)))]))
|
|
|
|
(define (powerset lst)
|
|
(append* ; flatten list of n sized subsets to just get subsets
|
|
(map (lambda (n)
|
|
(subsets-of lst n)) ; get subset of size n
|
|
(range 0 (+ 1 (length lst)))))) ; n from 0 to |lst|
|