|V| = 5, |E| = 7

adjacency matrix (1 = edge present)
    a b c d e 
  a 0 1 1 1 0 
  b 1 0 0 0 1 
  c 1 0 0 1 1 
  d 1 0 1 0 1 
  e 0 1 1 1 0 

adjacency lists
  a -> {b,c,d}
  b -> {a,e}
  c -> {a,d,e}
  d -> {a,c,e}
  e -> {b,c,d}

edge list
  (a,b) (a,c) (a,d) (b,e) (c,d) (c,e) (d,e) 

degrees (all three representations must agree)
  deg(a) = 3 3 3   agree
  deg(b) = 2 2 2   agree
  deg(c) = 3 3 3   agree
  deg(d) = 3 3 3   agree
  deg(e) = 3 3 3   agree
  sum of degrees = 14 = 2|E| = 14

adjacency queries
  a~b : yes yes yes
  a~e : no  no  no 
  c~e : yes yes yes
  b~d : no  no  no 

storage, counted in machine words
  edge list       14
  adjacency list  19
  adjacency matrix 25
