The Complexity of Finding Medians
نویسنده
چکیده
In this paper, PF(#P) is characterized in a similar manner to Krentel’s characterization [I<re88] of PF(NP). Let MidP be the class of functions that give the medians in the outputs of metric Turing machines. Then it is shown that every function in PF(#P) is polynomial time 1Turing reducible to a function in MidP and MidP PF(#P); that is, PF(#P) = PF(MidP[l]). Intuitively speaking, finding medians is as hard computationally as PF(#P); this forms a contrast to an intuitive interpretation of Krentel’s result that finding maximums (or minimums) is as hard as PF(NP). As applications of the result, several natural 5;complete problems for D#P are shown.
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