12.3.3 The Median Revisited
Let Al be a comparison-based algorithm that establishes the
median of a list of N elements, where N>=3 and N is odd.
We have shown in a previous section that there is an O(N) method
for solving this problem. Furthermore it is obvious that work
proportional to N is always required: all the elements have to
be looked at, and that requires at least ceiling(N/2)
comparisions.
This section improves our knowledge about the minimum amount of
work required to solve the problem. It proves that in the worst
case Al requires at least 3(N-1)/2 comparisons.
This material will not be covered this term.