2. Adjacency matrix

Matrix A $\mid$V$\mid$ x $\mid$V$\mid$, where

$$A[i,j] \;=\; \left\{ \begin{array}{ll} 1 & {\rm if} \;(i,j) \in E \\ 0 & {\rm otherwise} \end{array} \right.$$

Memory , Lookup O(1)

Both allow added satellite data easily

Adjacency list better for sparse graphs

Graph algorithms