Formatting fixed based on Keir's comments and extended the tests

internal/ceres/graph_algorithms.h

diff --git a/internal/ceres/graph_algorithms.h b/internal/ceres/graph_algorithms.h
index e83531d..3b42d93 100644
--- a/internal/ceres/graph_algorithms.h
+++ b/internal/ceres/graph_algorithms.h
@@ -50,9 +50,9 @@
 
   bool operator()(const Vertex& lhs, const Vertex& rhs) const {
     if (graph_.Neighbors(lhs).size() == graph_.Neighbors(rhs).size()) {
-      return (lhs < rhs);
+      return lhs < rhs;
     }
-    return (graph_.Neighbors(lhs).size() < graph_.Neighbors(rhs).size());
+    return graph_.Neighbors(lhs).size() < graph_.Neighbors(rhs).size();
   }
 
  private:

internal/ceres/graph_algorithms_test.cc

diff --git a/internal/ceres/graph_algorithms_test.cc b/internal/ceres/graph_algorithms_test.cc
index a67d7b7..d5d4843 100644
--- a/internal/ceres/graph_algorithms_test.cc
+++ b/internal/ceres/graph_algorithms_test.cc
@@ -172,22 +172,29 @@
   graph.AddVertex(2);
   graph.AddVertex(3);
 
-  // 0-1 2-3
-  // All vertices have degree 1.
+  // 0-1
+  //   |
+  // 2-3
+  // 0,1 and 2 have degree 1 and 3 has degree 2.
   graph.AddEdge(0, 1, 1.0);
   graph.AddEdge(2, 3, 1.0);
   VertexDegreeLessThan<int> less_than(graph);
 
   for (int i = 0; i < 4; ++i) {
-    EXPECT_FALSE(less_than(i,i))
-        << "Failing vertex: " << i;
+    EXPECT_FALSE(less_than(i,i)) << "Failing vertex: " << i;
     for (int j = 0; j < 4; ++j) {
       if (i != j) {
-        EXPECT_TRUE(less_than(i,j) ^ less_than(j,i))
+        EXPECT_TRUE(less_than(i, j) ^ less_than(j, i))
             << "Failing vertex pair: " << i << " " << j;
       }
     }
   }
+
+  for (int i = 0; i < 3; ++i) {
+    EXPECT_TRUE(less_than(i, 3));
+    EXPECT_FALSE(less_than(3, i));
+  }
 }
+
 }  // namespace internal
 }  // namespace ceres