#lang racket

(define/contract (find-peaks mountain)
  (-> (listof exact-integer?) (listof exact-integer?))
  (let _go ([i 1] [prev (car mountain)] [cur (cdr mountain)] [res '()])
    (if (= 1 (length cur)) res
      (let ([s (car cur)] [t (cadr cur)])
        (_go (+ i 1) s (cdr cur) (append res (if (and (> s prev) (> s t)) (cons i '()) '())))
        )
      )
    )
  )

(define (main)
  (define (r mountain exp)
    (printf
      "(find-peaks ~a) = ~a | Exp: ~a\n"
      mountain (find-peaks mountain) exp
      )
    )

  (r '(2 4 4) '())
  (r '(1 4 3 8 5) '(1 3))
  )

(main)