sicp_2.59-2.60

#lang racket

;;;;;;;;;;;;;;;;;;;;2.59
(define (element-of-set? x set)
  (cond ((null? set) false)
        ((equal? x (car set)) true)
        (else (element-of-set? x (cdr set)))))

(define (adjoin-set x set)
  (if (element-of-set? x set)
      set
      (cons x set)))

(define (intersection-set set1 set2)
  (cond ((or (null? set1) (null? set2)) '())
        ((element-of-set? (car set1) set2)
         (cons (car set1)
               (intersection-set (cdr set1) set2)))
        (else (intersection-set (cdr set1) set2))))

(define (union-set set1 set2)
  (cond ((null? set1) set2)
        ((null? set2) set1)
        ((element-of-set? (car set1) set2)
         (union-set (cdr set1) set2))
        (else (cons (car set1)
                    (union-set (cdr set1) set2)))))

;;;;;;;;;;;;;;;;;;;2.60
(define (new-element-of-set? x set)
  (cond ((null? set) false)
        ((equal? x (car set)) true)
        (else (element-of-set? x (cdr set)))))

(define (new-adjion-set x set)
  (cons x set))

(define (new-union-set set1 set2)
  (append set1 set2))

(define (new-intersection-set set1 set2)
 (cond ((or (null? set1) (null? set2)) '())
        ((element-of-set? (car set1) set2)
         (cons (car set1)
               (intersection-set (cdr set1) set2)))
        (else (intersection-set (cdr set1) set2))))

;;;;;;;;;;;;;;;;;test
(union-set '(1 2 3 4) '(0 3 5 1))
(new-union-set '(1 2 3 2 4) '(3 4 3 2 1 5))
(new-intersection-set '(1 3 3 2 4) '(2 3 2 2 4 5 1))
;;;;;;;;;;;;;;;;adjion和union分别变为O（1）和O（n）
;;;;;;;;;;;;;;;;其他不变