Selection of Best Sorting Algorithm for a Particular Problem

A disk recording and/or reproducing apparatus includes: a loading mechanism for drawing a disk having been inserted through an opening portion into the apparatus or drawing the disk having been held in the apparatus out of the opening portion; and an opening/closing sheet having first and second opening/closing portions, the first and second opening/closing portions being deformed by the disk to thereby open/close the opening portion. At least one of the first and second opening/closing portions has at least one deforming portion for facilitating the deformation of the opening/closing portion when the opening/closing portion is deformed by the disk carried by the loading mechanism.