Add challenge case for #87

Author: MiSawa

src/maxflow.rs

@@ -320,4 +320,15 @@ mod test {
 
         assert_eq!(graph.flow(s, t), 2);
     }
+
+    #[test]
+    fn test_dont_repeat_same_phase() {
+        let n = 100_000;
+        let mut graph = MfGraph::new(3);
+        graph.add_edge(0, 1, n);
+        for _ in 0..n {
+            graph.add_edge(1, 2, 1);
+        }
+        assert_eq!(graph.flow(0, 2), n);
+    }
 }