Editing Kidney swaps (section)

= The Kidney-swapping Algorithm =

When someone needs a new kidney a transplant from a friend or relative is far more likely to be a good match. The problem is that a donor isn’t always compatible and waiting lists for a new kidney can be quite long.

An innovation solution to this problem is the kidney-swapping algorithm: instead of having the donors match up to the recipients directly they form chains of donors who swap with a stranger in exchange for having another stranger swapping with their friend or family - or indirect matching.

You can apply this same algorithm to pairing up traders more efficiently on an exchange. Consider this example:

<blockquote>Alice: has 10 doge, wants 10 litecoin Bob: has 10 bitcoin, wants 10 doge Eve: has 10 litecoin, wants 10 bitcoin
</blockquote>
Here – none of the traders can be matched up directly with a limit order because none of them directly have what the other wants. However, if we do a kidney-swap - the trades can still happen:

Eve sends to Alice who sends to Bob who sends to Eve … and everyone gets something they want.

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