HtDP taught us how to check if there exists path(s) from one node to another.
I tried to implement accumulating all the paths between two nodes as:
```racket
(define (find-paths origin dest G path)
(cond
[(equal? origin dest) (reverse (cons dest path))]
[else
(find-paths/all (neighbors origin G) dest G (cons origin path))]))
(define (find-paths/all lons dest G path)
(cond
[(empty? lons) '(#f)]
[else
(map (λ (n) (find-paths n dest G path)) lons)]))
```
However, when I tested it by
```racket
(define sample-graph
'((A (B E))
(B (E))))
(define (neighbors origination G)
(cadr (assoc origination G)))
(find-paths 'A 'E sample-graph '())
```
The answer is: '(((A B E)) (A E))
In order to get the right answer, I have to write another `flatten` function as:
```racket
(define (flatten-path lop)
(cond
[(empty? lop) empty]
[(not (list? (caar lop))) (cons (first lop) (flatten-path (rest lop)))]
[else
(append (flatten-path (first lop)) (flatten-path (rest lop)))]))
(filter (λ (path) (not (boolean? (car path)))) (flatten-path (find-paths 'A 'E
sample-graph '())))
```
And now it works.
I was wondering if maybe I could improve it?
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