;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-intermediate-lambda-reader.ss" "lang")((modname graph) (read-case-sensitive #t) (teachpacks ((lib "master.ss" "teachpack" "htdp") (lib "draw.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "master.ss" "teachpack" "htdp") (lib "draw.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp")))))

;; a graph is represented as a list of lists,
;; each list contains a node and a list of its neighbors
;; (adjacency list)
(define Graph 
  '((A (B E))
    (B (E F))
    (C (D))
    (D ())
    (E (C F))
    (F (D G))
    (G ())))

Graph

;; neighbors: node graph
;; To find all neightbors of a node in a graph
(define (neighbors node G)
   ;;; your code goes here   
)

(check-expect (neighbors 'E Graph) (list 'C 'F))
(check-expect (neighbors 'G Graph) empty)
(check-error (neighbors 'X Graph) "neighbors: No such node")


;; find-route : node node graph  ->  (listof node) or false
;; to create a path from origin to destination in G
;; if there is no path, the function produces false
(define (find-route origin destination G)
  (cond
    [(symbol=? origin destination) (list destination)]
    [else (local ((define possible-route 
		    (find-route/list (neighbors origin G) destination G)))
	    (cond
	      [(boolean? possible-route) false]
	      [else (cons origin possible-route)]))]))

;; find-route/list : (listof node) node graph  ->  (listof node) or false
;; to create a path from some node on lo-Os to D
;; if there is no path, the function produces false
(define (find-route/list lo-Os D G)
  (cond
    [(empty? lo-Os) false]
    [else (local ((define possible-route (find-route (first lo-Os) D G)))
	    (cond
	      [(boolean? possible-route) (find-route/list (rest lo-Os) D G)]
	      [else possible-route]))]))

;; write results in check-expect for these cases:
(find-route 'B 'G Graph)
(find-route 'C 'A Graph)