From 22a5720da0c27ee9c0bce866049712036efcbe8e Mon Sep 17 00:00:00 2001
From: Sergiu Ivanov <sivanov@colimite.fr>
Date: Sun, 7 Nov 2021 21:49:32 +0100
Subject: [PATCH] Add maxflow.

---
 graph.rkt | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/graph.rkt b/graph.rkt
index 0e0a995..a4b990a 100644
--- a/graph.rkt
+++ b/graph.rkt
@@ -45,6 +45,8 @@
            coloring coloring/greedy coloring/brelaz
            order-smallest-last valid-coloring?
 
+           maxflow
+
            graphviz)
 
   ;; Wrap the opaque graph structure coming from the generic
@@ -228,6 +230,10 @@
   (define (valid-coloring? g coloring)
     (g:valid-coloring? (gg g) coloring))
 
+  ;; 9 Maximum Flow
+  (define (maxflow g source sink)
+    (g:maxflow (gg g) source sink))
+
   ;; 10 Graphviz
   (define (graphviz g #:output [output #f] #:colors [colors #f])
     (g:graphviz (gg g) #:output output #:colors colors)))
@@ -345,6 +351,9 @@
   [order-smallest-last (-> Graph (Listof Any))]
   [valid-coloring? (-> Graph (HashTable Any Number) Boolean)]
 
+  ;; 9 Maximum Flow
+  [maxflow (-> Graph Any Any (HashTable (List Any Any) Number))]
+
   ;; 10 Graphviz
   [graphviz (->* (Graph)
                  (#:output Output-Port
@@ -565,6 +574,11 @@
 
     (check-true (valid-coloring? g0 #hash((a . 0) (b . 1) (c . 0) (d . 2)))))
 
+  (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))))
+
   (test-case "10 Graphviz"
     (define g (directed-graph '((a b) (b c))))
     (check-equal? (graphviz g)