Explanation : In quicksort a set of number is reduced to sorting
two smaller set. We take first element as key
value and combine all other with this. A pivot
element which splits list into two sublists each of
which at least one fifth of element only (B), i.e.
T(n) ≤ T(n/5) + T(4n/5) + n the problem.
Alternately
If one sublist contains 1/5 elements other contains
4/5 elements.
If T(n) number of comparisons for sorting n
elements.
So, for 1/5 elements = T(1/5n)
and for 4/5 elements = T(4n/5)
So, T(n) ≤ T(n/5) + T(4n/5) + n.
Here, n = time to spilt