Recognizing when to use the modulus operator

Question

I know the modulus (%) operator calculates the remainder of a division. How can I identify a situation where I would need to use the modulus operator?

I know I can u

Answer 1

Best use of modulus operator I have seen so for is to check if the Array we have is a rotated version of original array.

A = [1,2,3,4,5,6] B = [5,6,1,2,3,4]

Now how to check if B is rotated version of A ?

Step 1: If A's length is not same as B's length then for sure its not a rotated version.

Step 2: Check the index of first element of A in B. Here first element of A is 1. And its index in B is 2(assuming your programming language has zero based index). lets store that index in variable "Key"

Step 3: Now how to check that if B is rotated version of A how ??

This is where modulus function rocks :

for (int i = 0; i< A.length; i++)
{

// here modulus function would check the proper order. Key here is 2 which we recieved from Step 2
   int j = [Key+i]%A.length;

   if (A[i] != B[j])
   {
     return false;
   }
}

return true;