scheme - 取出完美正方形

Question

你将如何编写一个代码来从列表中删除完美的正方形，只使用过滤器和整数？我相信这是内置的方案。例如。(take-out-perfect-squares '(1 2 9 16 5 64)) 应该返回 (2 5) 因为该列表中其他所有内容的平方根返回一个整数。谢谢！

Answer 1

(define remove-perfect-square-helper
  (lambda (x y)
    (if (null? x)
        (reverse y)
    (if (integer? (sqrt (car x)))
        (remove-perfect-square-helper (cdr x) y)
        (remove-perfect-square-helper (cdr x) (cons (car x) y))))))

(define remove-perfect-square
        (lambda (x)
          (remove-perfect-square-helper x '())))


(define x '(1 2 9 16 5 64))

(remove-perfect-square x)

Answer 2

(define (take-out-perfect-squares l)
  (cond ((null? l) '())
        ((integer? (sqrt (car l)))
         (take-out-perfect-squares (cdr l)))
        (else
         (cons (car l) (take-out-perfect-squares (cdr l))))))