//Instead of using the classic recursive approach i.e. x*pow(x, n-1) just have (x*x), i.e., pow(x*x, n/2). //This will make the TC logarithmic instead of linear. //Just take care of the edge cases ...

//We are basically storing sum%k and storing it in the hashmap and checking it. //Math logic is that the overall sum will get cancelled out because of modulo ...