22 lines
793 B
Racket
22 lines
793 B
Racket
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#lang racket
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(define (balance lst)
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(define (helper lst counter)
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(cond
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[(empty? lst) counter] ;;base case
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[(list? (first lst)) (helper (rest lst) counter)] ;;unwrap list
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[(eq? (first lst) 'debit) (helper (rest lst) (- counter last))] ;;if debit subtract the amount
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[(eq? (first lst) 'credit) (helper (rest lst) (+ counter last))] ;;if credit add the amount
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[else (helper (rest lst) counter)]
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)
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)
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(helper lst 0)
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)
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;; Racket
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(module+ test
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(require rackunit)
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(check-equal? (balance (list (list 'credit 5))) 5)
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(check-equal? (balance (list '(debit 5))) -5)
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(check-equal? (balance '((debit 11) (credit 3))) -8)
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(check-equal? (balance '((debit 3) (credit 5))) 2)
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(check-equal? (balance '((debit 5) (credit 23) (debit 23) (credit 5))) 0))
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