Expositionsort

Expositionsort is a term used in computer science to describe a class of sorting methods that sort by progressively exposing elements’ keys across several passes. The idea is to refrain from placing every item in its final position in a single decision, and instead reveal information about the order of elements step by step, allowing previously exposed items to constrain the placement of the remaining ones. The name reflects this notion of “exposing” or “exposition” of order information.

In typical implementations, the algorithm works by performing a sequence of expositions. In each pass, a chosen key or a small set of keys is exposed, and the input list is partitioned or reorganized so that items with smaller exposed keys appear before those with larger ones. Items whose relative order cannot yet be determined remain in an unexposed region for subsequent passes. After enough expositions, every element has a final, stable position. Stable variants preserve the relative order of equal keys, if the exposure mechanism is designed accordingly.

Performance of Expositionsort depends on how the expositions are chosen. With a balanced exposition strategy, the average running time can approach O(n log n), while pathological choices may degrade to O(n^2). Some implementations use additional storage to realize a stable, multi-pass variant, while in-place versions trade stability for space.

Expositionsort is mainly discussed in theoretical or teaching contexts to illustrate the effect of progressive information revelation in sorting, rather than as a dominant practical algorithm. See also stable sort, bucket sort, and quicksort.