Add dfs.

graph.rkt

@@ -33,6 +33,7 @@
            matrix-graph?
 
            bfs fewest-vertices-path
+           dfs
 
            graphviz)
 
@@ -117,6 +118,10 @@
   (define (fewest-vertices-path G source target)
     (g:fewest-vertices-path (gg G) source target))
 
+  ;; 4.2 Depth-first Search
+  (define (dfs g)
+    (g:dfs (gg g)))
+
   ;; 10 Graphviz
   (define (graphviz g #:output [output #f] #:colors [colors #f])
     (g:graphviz (gg g) #:output output #:colors colors)))
@@ -170,6 +175,11 @@
                              (Mutable-HashTable Any Any)))]
   [fewest-vertices-path (-> Graph Any Any (U (Listof Any) False))]
 
+  ;; 4.2 Depth-first Search
+  [dfs (-> Graph (Values (Mutable-HashTable Any Number)
+                         (Mutable-HashTable Any Any)
+                         (Mutable-HashTable Any Number)))]
+
   ;; 10 Graphviz
   [graphviz (->* (Graph)
                  (#:output Output-Port
@@ -251,7 +261,17 @@
     (check-equal? (hash->ordered-list bfs-lens) '((a . 0) (b . 1) (c . 2)))
     (check-equal? (hash->ordered-list bfs-tree) '((a . #f) (b . a) (c . b)))
     (check-equal? (fewest-vertices-path (directed-graph '((a b) (b c) (c d))) 'a 'd)
-                  '(a b c d)))
+                  '(a b c d))
+
+    ;; 4.2 Depth-first Search
+    (define-values (dfs-discovery dfs-pred dfs-finish)
+      (dfs (directed-graph '((a b) (a c) (b d) (c d)))))
+    (check-equal? (hash->ordered-list dfs-discovery)
+                  '((a . 4) (b . 5) (c . 0) (d . 1)))
+    (check-equal? (hash->ordered-list dfs-pred)
+                  '((a . #f) (b . a) (c . #f) (d . c)))
+    (check-equal? (hash->ordered-list dfs-finish)
+                  '((a . 7) (b . 6) (c . 3) (d . 2))))
 
   (test-case "10 Graphviz"
     (define g (directed-graph '((a b) (b c))))