Add benchmark

Author: korthaj

strong_test.go

@@ -1,6 +1,7 @@
 package graph
 
 import (
+	"math/rand"
 	"testing"
 )
 
@@ -31,3 +32,16 @@ func TestStrongComponents(t *testing.T) {
 		t.Errorf("StronglyConnected %s", mess)
 	}
 }
+
+func BenchmarkStrongComponents(b *testing.B) {
+	n := 1000
+	b.StopTimer()
+	g := New(n)
+	for i := 0; i < n; i++ {
+		g.Add(rand.Intn(n), rand.Intn(n))
+	}
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		_ = StrongComponents(g)
+	}
+}