A number of combinatorial problems of interest to computational economists, such as some two-sided matching problems, belong to the complexity class NP. The best known solutions to these problems require exponential computation time in the size of the input, and are intractable in practice...

Previous researchers have modelled the decision to accept a donor organ for transplantation as a Markov decision problem, the solution to which is often a control-limit optimal policy: accept any organ whose match quality exceeds some health-dependent threshold; otherwise, wait for another. When...