Saving 2 elements at single index

 Yes we can save two numbers at one place by using simple mathematical formula.

The formula : 

dividend=divisor*quotient+remainder

Rotate an array in O(n)

Step 1 :
Reverse the first k elements.

Step 2:

Reverse the k+1 to n-1 elements.

Step 3:

Reverse the whole array.

Prefect!!!

Example :

arr=[1,2,3,4,5] , k=2

expected output : [3,4,5,1,2]

step 1:

[2,1,3,4,5]

step 2:

[2,1,5,4,3]

step 3:

[3,4,5,1,2]

Got it!

Check rotation count in a sorted array

To check for the rotation count in a sorted array :

we can check the index of the least element :
the index is the rotation count of the array.

For example :
[2,3,4,1]

index of 1 is 4, therefore rotation count is 4 to the right.