;делит списки по 0 1 2
(define (splitting lst n r1 r2 r3 l1 l2 l3)
  (if (and (= n l1)  (= n l2) (= n l3)) (list r1 r2 r3)
       ( cond ( (= 0 (remainder (car lst) 3)) (splitting (cdr lst) n (cons (car lst) r1) r2 r3 (+ 1 l1) l2 l3))
             ( (= 1 (remainder (car lst) 3)) (splitting (cdr lst) n r1 (cons (car lst) r2) r3 l1 (+ 1 l2) l3))
             ( (= 2 (remainder (car lst) 3)) (splitting (cdr lst) n r1 r2 (cons (car lst) r3) l1 l2 (+ 1 l3))))))
(define (main lst N)
  (define (threelist lst res)
    (if (empty? (car lst)) res
        (threelist (list(cdar lst) (cdadr lst) (cdaddr lst)) (cons (list(caar lst) (caadr lst) (caaddr lst)) res))))
  (threelist (splitting lst N '() '() '() 0 0 0) '()))


; 3 task

(define (treelist tree)
  (if (empty? tree) '()
      (append (treelist (cadr tree)) (cons (car tree) (treelist (caddr tree))))))
(define (Maxtree lst)
  (define (searchmax lst mx n)
    (if (empty? lst) n
    (cond ((< (car lst) mx) (searchmax (cdr lst) mx n))
        ((= (car lst) mx) (searchmax ( cdr lst) mx (+ 1 n)))
          ((> (car lst) mx) (searchmax (cdr lst)(car lst) (= 1 n))))))
  (searchmax (treelist lst)(car(treelist lst)) 0 ))


; 4 task

(define (tree-list tree)
 (if (empty? tree) 0
     (+ ( if (and (empty? ( cadr tree)) (empty? (caddr tree))) 1 0)
        (tree-list (cadr tree)) (tree-list (caddr tree)))))



;5 задача
 (define (Twochildren tree)
    (define (parent tree)
       (if (empty? tree) 0
   (let ((left (parent (cadr tree)))
        (right (parent (caddr tree))))
    (if (or (not left)
            (not right)) #f
    (if (> (abs (- right left)) 0) #f
    (+ (max left right) 1))))))
       (number? (parent tree)))