A company registers an IPO on a website sellshares.com. All the shares on this website are available for bidding for a particular time frame called the bidding window. At the end of the bidding window an auction logic is used to decide how many of the available shares go to which bidder until all the shares that are available have been allotted, or all the bidders have received the shares they bid for, whichever comes earlier.
This is a companion discussion topic for the original entry at https://algo.monster/problems/citadel-oa-initial-public-offering/