  We investigate the formation channels of the intracluster light (ICL) and the
brightest cluster galaxy (BCG) in clusters at $z=0$. For this, we perform
multi-resolution cosmological N-body simulations using the "Galaxy Replacement
Technique" (GRT). We study the formation channels of the ICL and BCG as a
function of distance from the cluster center and the dynamical state of the
clusters at $z=0$. To do this, we trace back the stars of the ICL and BCG, and
identify the stellar components in which they existed when they first fell into
the clusters. We find that the progenitors of the ICL and BCG in the central
region of the cluster fell earlier and with a higher total mass ratio of the
progenitors to the cluster compared to the outer region. This causes a negative
radial gradient in the infall time and total mass ratio of the progenitors.
Although stellar mass of the progenitors does not show the same radial gradient
in all clusters, massive galaxies ($M_{\rm{gal}} > 10^{10}~M_{\odot}~h^{-1}$)
are the dominant formation channel of the ICL and BCG for all clusters, except
for our most relaxed cluster. For clusters that are dynamically more unrelaxed,
we find that the progenitors of the ICL and BCG fall into their clusters more
recently, and with a higher mass and mass ratio. Furthermore, we find that the
diffuse material of massive galaxies and group-mass halos that is formed by
pre-processing contributes significantly to the ICL in the outer region of the
unrelaxed clusters.
