Add bipartite?.

graph.rkt

@@ -45,7 +45,7 @@
            coloring coloring/greedy coloring/brelaz
            order-smallest-last valid-coloring?
 
-           maxflow
+           maxflow bipartite?
 
            graphviz)
 
@@ -233,6 +233,8 @@
   ;; 9 Maximum Flow
   (define (maxflow g source sink)
     (g:maxflow (gg g) source sink))
+  (define (bipartite? g)
+    (g:bipartite? (gg g)))
 
   ;; 10 Graphviz
   (define (graphviz g #:output [output #f] #:colors [colors #f])
@@ -353,6 +355,7 @@
 
   ;; 9 Maximum Flow
   [maxflow (-> Graph Any Any (HashTable (List Any Any) Number))]
+  [bipartite? (-> Graph (U (List (Listof Any) (Listof Any)) False))]
 
   ;; 10 Graphviz
   [graphviz (->* (Graph)
@@ -577,7 +580,11 @@
   (test-case "9 Maximum Flow"
     (define g0 (weighted-graph/directed '((1 a b) (2 a c) (3 b d) (3 c d))))
     (check-equal? (hash->ordered-list (maxflow g0 'a 'd))
-                  '(((a b) . 1) ((c d) . 2) ((b d) . 1) ((a c) . 2))))
+                  '(((a b) . 1) ((c d) . 2) ((b d) . 1) ((a c) . 2)))
+
+    (define g1 (directed-graph '((a b) (c b))))
+    (check-false (bipartite? g0))
+    (check-equal? (bipartite? g1) '((b) (a c))))
 
   (test-case "10 Graphviz"
     (define g (directed-graph '((a b) (b c))))