FInding minimum of a binary search tree in Racket

Question

So, i am trying to find the least value of a binary search tree in racket and i keep getting this error:

cadr: contract violation expected: (cons/c any/c pair?) given: 'null

My code is the following:

(define minimum (λ (tree) (if (null? tree) null (if (null? (cadr tree)) (car tree) (minimum (cadr tree)))))

Each node has the structure (value, left, right).

Óscar López · Accepted Answer · 2016-03-17 19:30:43Z

1

It looks like a problem with your test data, not the minimum procedure itself. For instance, this works for me:

(define tree
  (list 5 (list 3 (list 1 null null)
                  (list 4 null null))
          (list 6 null null)))

(minimum tree)
=> 1

answered Mar 17, 2016 at 19:30

Óscar López

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