(load "2.40.txt") ; for unique-pairs
; Find (i, j, k) st
; 1 <= i < j < k <= n
; i + j + k = s

(define (three-sum n s)
  (define (solution? triple)
    (let ((i (car triple))
          (j (cadr triple))
          (k (caddr triple)))
    (and (> i 0) (< i j))))
  (filter solution?
          (map (lambda (pair)
                 (let ((k (car pair))
                       (j (cadr pair)))
                   (list (- s (+ j k)) j k)))
               (unique-pairs n))))