The adjacency list representation of a graph consists of 
lists one for each vertex 
, 
, which gives the vertices to which 
is adjacent. The adjacency lists of a graph 
may be computed in the Wolfram
Language using
AdjacencyList[g, #]& /@ VertexList[g]
and a graph may be constructed from adjacency lists 
using
Graph[UndirectedEdge @@@ Union[
Sort /@ Flatten[
MapIndexed[{#, #2[[1]]}&, l, {2}],
1]]]
