  Leavitt path algebras associate to directed graphs a $\mathbb Z$-graded
algebra and in their simplest form recover the Leavitt algebras $L(1,k)$. In
this note, we first study this $\mathbb Z$-grading and characterize the
($\mathbb Z$-graded) structure of Leavitt path algebras, associated to finite
acyclic graphs, $C_n$-comet and multi-headed graphs. The last two type are
examples of graphs whose Leavitt path algebras are strongly graded. We
characterize Leavitt path algebras which are strongly graded, along the way
obtaining classes of algebras which are group rings or crossed-products. In an
attempt to generalize the grading, we introduce weighted Leavitt path algebras
associated to directed weighted graphs which have natural
$\textstyle{\bigoplus} \mathbb Z$-grading and in their simplest form recover
the Leavitt algebras $L(n,k)$. We then establish some basic properties of these
algebras.
