As contig numbers must always be from 1 to N, where N is the number of contigs, if we remove a particular contig, we need to ensure we still have contigs 1 to N-1. In thise case, deleting contig x, where x != N, will mean that we have a hole (at x) which can be filled by moving N down to x.
To illustrate in an algorithm we have the following; Given N contigs and a request to delete contig x.
io_delete_contig
operation goes as we're already assuming the data on
this contig has gone elsewhere.
Hence it is important to remember that after an io_delete_contig
the
contig numbers may not be the same as before the call.