On Lower Bounds for Selection Problems

Abstract

Let V i (n) be the minimum number of binary comparisons that are required to determine the i-th largest of n elements drawn from a totally ordered set. In this thesis we use adversary strategies to prove lower bounds on V i (n). For i = 3, our lower bounds determine V 3(n) precisely for infinitely many values of n,and determine V 3(n) to within 2 for all n.