highlighted in blue the positions removed are drawn with dashed lines maintaining the top-most level skip-list must maintain reference to the start position (the top-mostleft position in sas an instance variableand must have policy for any insertion that wishes to continue inserting new entry past the top level of there are two possible courses of action we can takeboth of which have their merits one possibility is to restrict the top levelhto be kept at some fixed value that is function of nthe number of entries currently in the dictionary (from the analysis we will see that max , log is reasonable choiceand picking logn is even saferimplementing this choice means that we must modify the insertion algorithm to stop inserting new position once we reach the top-most level (unless logn log( in which case we can now go at least one more levelsince the bound on the height is increasingthe other possibility is to let an insertion continue inserting new position as long as heads keeps getting returned from the random number generator this is the approach taken in algorithm skipinsert of code fragment as we show in the analysis of skip liststhe probability that an insertion will go to level that is more than (lognis very lowso this design choice should also work either choice will still result in the expected (logntime to perform searchinsertionand removalhoweverwhich we show in the next section probabilistic analysis of skip lists as we have shown aboveskip lists provide simple implementation of an ordered dictionary in terms of worst-case performancehoweverskip lists are not superior data structure in factif we don' officially prevent an insertion from continuing significantly past the current highest levelthen the insertion algorithm