How do memory-championship competitors memorise a shuffled deck of cards?

They convert cards to images (usually via a Person-Action-Object system) and place them along a well-drilled palace, then walk it to recall the order.

The full stack: a fixed image system maps each card (or pair/triple of cards) to a memorable image, and a rehearsed palace stores those images in sequence. Top competitors memorise a 52-card deck in well under a minute this way. The palace supplies the order; the image system supplies fast, collision-free encoding. Digits work identically, using the Major System or a number-PAO.