Add bfs.

graph.rkt

@@ -32,6 +32,8 @@
            undirected-graph directed-graph
            matrix-graph?
 
+           bfs
+
            graphviz)
 
   ;; Wrap the opaque graph structure coming from the generic
@@ -108,6 +110,11 @@
   (define (matrix-graph? g)
     (g:matrix-graph? (gg g)))
 
+  ;; 4 Basic Graph Functions
+  ;; 4.1 Breadth-first Search
+  (define (bfs g source)
+    (g:bfs (gg g) source))
+
   ;; 10 Graphviz
   (define (graphviz g #:output [output #f] #:colors [colors #f])
     (g:graphviz (gg g) #:output output #:colors colors)))
@@ -155,6 +162,11 @@
   ;; 2.3 Matrix Graphs
   [matrix-graph? (-> Graph Boolean)]
 
+  ;; 4 Basic Graph Functions
+  ;; 4.1 Breadth-first Search
+  [bfs (-> Graph Any (Values (Mutable-HashTable Any Number)
+                             (Mutable-HashTable Any Any)))]
+
   ;; 10 Graphviz
   [graphviz (->* (Graph)
                  (#:output Output-Port
@@ -230,6 +242,12 @@
     ;; 2.3 Matrix Graphs
     (check-false (matrix-graph? (directed-graph '((a b) (b c))))))
 
+  (test-case "4 Basic Graph Functions"
+    ;; 4.1 Breadth-first Search
+    (define-values (bfs-lens bfs-tree) (bfs (directed-graph '((a b) (b c))) 'a))
+    (check-equal? (hash->ordered-list bfs-lens) '((c . 2) (a . 0) (b . 1)))
+    (check-equal? (hash->ordered-list bfs-tree) '((a . #f) (b . a) (c . b))))
+
   (test-case "10 Graphviz"
     (define g (directed-graph '((a b) (b c))))
     (check-equal? (graphviz g)