計劃。尾遞歸？

Question

下面提到的僞代碼的任何尾遞歸版本？謝謝 ！

(define (min list) 
    (cond 
    ((null? list) '()) 
    ((null? (cdr list)) (car list)) 
    (#t (let ((a (car list)) 
      (b (min (cdr list)))) 
     (if (< b a) b a))))) 

Answer 1

您應該閱讀fold higher-order functions。

Answer 2

定義一個幫助函數，它帶有一個列表和迄今爲止找到的最小元素（我們稱之爲b）。如果列表爲空，則應返回b，否則如果列表（a）的頭部小於b，則應返回(helper (cdr list) a)，否則返回(helper (cdr list) b)。現在我們可以將(min list)定義爲(helper (cdr list) (car list))。

Answer 3

(define (min list) 
    (let imin ((l (cdr list)) 
     (m (car list))) 
    (cond 
    ((null? l) m) 
    (else 
     (let ((a (car l))) 
     (imin (cdr l) 
       (if (< a m) a m))))))) 

Answer 4

(define (min ns) 
    (let loop ((ns-left ns) (min-so-far maxint)) 
    (if (null? ns-left) 
     min-so-far 
     (loop 
     (cdr ns-left) 
     (if (< (car ns-left) min-so-far) 
      (car ns-left) 
      min-so-far))))) 

Answer 5

(define (min list) 
    (min-helper list #f)) 

(define (min-helper list min-so-far) 
    (if (null? list) 
     min-so-far 
     (let ((m (car list))) 
      (if (eq? min-so-far #f) 
       (set! min-so-far m)) 
      (if (< m min-so-far) 
       (min-helper (cdr list) m) 
       (min-helper (cdr list) min-so-far)))))