table adjacency matrix the vertices are used as headings for both rows and columns an edge between two vertices is indicated by the absence of an edge is (you could also use boolean true/false values as you can seevertex is adjacent to all three other verticesb is adjacent to and dc is adjacent only to aand is adjacent to and in this examplethe "connectionof vertex to itself is indicated by so the diagonal from upper left to lower righta- to -dwhich is called the identity diagonalis all the entries on the identity diagonal don' convey any real informationso you can equally well put along itif that' more convenient in your program note that the triangular-shaped part of the matrix above the identity diagonal is mirror image of the part belowboth triangles contain the same information this redundancy may seem inefficientbut there' no convenient way to create triangular array in most computer languagesso it' simpler to accept the redundancy consequentlywhen you add an edge to the graphyou must make two entries in the adjacency matrix rather than one the adjacency list the other way to represent edges is with an adjacency list the list in adjacency list refers to linked list of the kind we examined in "linked lists actuallyan adjacency list is an array of lists (or sometimes list of listseach individual list shows what vertices given vertex is adjacent to table shows the adjacency lists for the graph of figure table adjacency lists vertex list containing adjacent vertices --> --> --> --> in this tablethe --symbol indicates link in linked list each link in the list is vertex here the vertices are arranged in alphabetical order in each listalthough that' not really necessary don' confuse the contents of adjacency lists with paths the adjacency list shows which vertices are adjacent to--that isone edge away from-- given vertexnot paths from vertex to vertex