code javascript: Compute how many types of items can stay in a storeroom after removing R consecutive items.

Task description

A storeroom is used to organize items stored in it on N shelves. Shelves are numbered from $0$ to N$1.$ The K$-$th shelf is dedicated to items of only one type, denoted by a positive integer A$[$K$].$

Recently it was decided that it is necessary to free R consecutive shelves. Shelves cannot be reordered. What is the maximum number of types of items which still can be stored in the storeroom after freeing R consecutive shelves?

Write a function:

function solution$($A$,$ R$)$;

that, given an array A of N integers representing types of items stored on storeroom shelves, and an integer R representing the number of consecutive shelves to be freed, returns the maximum number of different types of items that can be stored in the storeroom after freeing R consecutive shelves.

Examples:

$1.$ Given A $=[2,1,2,3,2,2]$ and R $=3,$ your function should return $2.$ It can be achieved, for example, by freeing shelves $2,3$ and $4($shelves are numbered from $0).$

$2.$ Given A $=[2,3,1,1,2]$ and R $=2,$ your function should return $3.$ All three types can still be stored by freeing the last two shelves.

$3.$ Given A $=[20,10,10,10,30,20]$ and R $=3,$ your function should return $3.$ It can be achieved by freeing the first three shelves.

$4.$ Given A $=[1,100000,1]$ and R $=3,$ your function should return $0.$ All shelves need to be freed.

Write an efficient algorithm for the following assumptions:

$$ N is an integer within the range $[1.\mathrm{.}100,000]$;

$$ R is an integer within the range $[1..$N$]$;

$$ each element of array A is an integer within the range $[1.\mathrm{.}100,000].$