logGraph [ u ] [ v ] is non zero only for adjacent vertices of m mstSet [ v ] is false for vertices not yet included in MST Update the key only if logGraph [ u ] [ v ] is smaller than key [ v ]
if ( logGraph [ u ] [ v ] > 0 && mstSet [ v ] == false && logGraph [ u ] [ v ] < key [ v ] ) parent [ v ] = u , key [ v ] = logGraph [ u ] [ v ] ; }