/
2.65.scm
73 lines (63 loc) · 2.59 KB
/
2.65.scm
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(define (make-tree entry left right) (list entry left right))
(define (entry tree) (car tree))
(define (left-branch tree) (cadr tree))
(define (right-branch tree) (caddr tree))
(define (tree->list tree)
(define (copy-to-list tree result-list)
(if (null? tree)
result-list
(copy-to-list (left-branch tree)
(cons (entry tree)
(copy-to-list (right-branch tree)
result-list)))))
(copy-to-list tree '()))
(define (list->tree elts)
(define (partial-tree elts n)
(if (= n 0)
(cons '() elts)
(let* ((left-size (quotient (- n 1) 2))
(left-result (partial-tree elts left-size))
(left-tree (car left-result))
(non-left-elts (cdr left-result))
(this-entry (car non-left-elts))
(right-size (- n (+ left-size 1)))
(right-result (partial-tree (cdr non-left-elts) right-size))
(right-tree (car right-result))
(remaining-elts (cdr right-result)))
(cons (make-tree this-entry
left-tree
right-tree)
remaining-elts))))
(car (partial-tree elts (length elts))))
(define (union-list set1 set2)
(cond ((null? set1) set2)
((null? set2) set1)
(else
(let ((car1 (car set1))
(car2 (car set2))
(cdr1 (cdr set1))
(cdr2 (cdr set2)))
(cond ((= car1 car2) (cons car1 (union-list cdr1 cdr2)))
((< car1 car2) (cons car1 (union-list cdr1 set2)))
((> car1 car2) (cons car2 (union-list set1 cdr2))))))))
(define (union-set tree1 tree2)
(let ((list1 (tree->list tree1))
(list2 (tree->list tree2)))
(list->tree (union-list list1 list2))))
(define (intersection-list set1 set2)
(if (or (null? set1) (null? set2))
'()
(let ((car1 (car set1))
(car2 (car set2))
(cdr1 (cdr set1))
(cdr2 (cdr set2)))
(cond ((= car1 car2) (cons car1 (intersection-list cdr1 cdr2)))
((< car1 car2) (intersection-list cdr1 set2))
((> car1 car2) (intersection-list set1 cdr2))))))
(define (intersection-set tree1 tree2)
(let ((list1 (tree->list tree1))
(list2 (tree->list tree2)))
(list->tree (intersection-list list1 list2))))
(tree->list (list->tree '(1 3 5 7 9)))
(tree->list (union-set (list->tree '(1 3 5 7 9)) (list->tree '(2 3 5 7))))
(tree->list (intersection-set (list->tree '(1 3 5 7 9)) (list->tree '(2 3 5 7))))