[Cleanup] Use C++11

src/one-body-sample.cc

@@ -391,8 +391,8 @@ int main(int argc, char *argv[]) {
       // condition match up at t=0
       double v_initial_const;
       velocityDirichletFunction.evaluate(0.0, v_initial_const);
-      for (size_t i = 0; i < v_initial.size(); ++i)
-        v_initial[i][0] = v_initial_const;
+      for (auto &x : v_initial)
+        x[0] = v_initial_const;
     }
     VectorType a_initial(finestSize);
     a_initial = 0.0;