QuickSelect is an algorithm for finding the

k

k$-$th smallest element in an unsorted array of size

n

n$.$ It is similar to

QuickSort

QuickSort but focuses on one partition per recursive iteration, making it more efficient for selection tasks:

$1.$

algorithm

$1.$ algorithm

QuickSelect

$($

A

:

array

$,$

k

:

Z

$>=$

$0$

$,$

l

:

Z

$>=$

$0$

$,$

r

:

Z

$>=$

$0$

$)$

QuickSelect$($A:array,k:Z

$>=0$

$$

$,$l:Z

$>=0$

$$

$,$r:Z

$>=0$

$$

$)$

$2.$

if

l

$=$

r

then

$2.$ if l$=$r then

$3.$

return

A

$[$

l

$]$

$3.$ return A$[$l$]$

$4.$

end

if

$4.$ end if

$5.$

m

$$

partition

$($

A

$,$

l

$,$

r

$)$

$5.$ m$$partition$($A$,$l$,$r$)$

$6.$

if

k

$=$

m

then

$6.$ if k$=$m then

$7.$

return

A

$[$

m

$]$

$7.$ return A$[$m$]$

$8.$

else

if

k

$<$

m

then

$8.$ else if k

$0$

C

p

$$

$>0,$ and

n

n is the size of the given array.