PivotList $($ list, first, last$)$

list the elements to work with

first the index of the first element

last the index of the last element

Pivotvalue $=$ list $[$ first $]$

lower $=$ first

upper $=$ last $+1$

do

do upper $=$ upper $-1$ until list$[$upper$]$ S Pivotvalue

do lower $=$ lower $+1$ until list $[$lower$]$ Pivotvalue

Swap $($ list $[$ upper $],$ list $[$ lower $])$

until lower $$ upper

$//$ undo the extra exchange

Swap $($ list $[$ upper $],$ list $[$ lower $])$

$//$ move pivot point into correct place

Swap$($ list $[$ first $],$ list $[$ upper $])$

return upper

Trace the operation of Quicksort on the list $,7,35,4.$ Show the list order and the stack of $($first$,$ last, pivot$)$ values at the start of every call. Count the number of comparisons and swaps that are done.

a$.$ Do Question $1$ using this alternative method for PivotList. Do question a$.$