I cannot understand what is wrong with my code here. I have applied sliding window algorithm over a range of possible length say k belonging to [A,B]. I just don’t understand where I went wrong. Please help me out.
@alathedarkwiz Your algorithm is completely right 
The only mistake you did is that you didn’t set the precision of the answer. It’s mentioned in the problem to set the decimal places to atleast 6.
Add a line in starting of your main();
cout<<fixed<<setprecision(10);
You’ll get an AC
I’ve set the precision to 10 decimal places. You can set to any above 5
Okay just another question “long long arr[n+1];” is correct right?
Seems to be correct. But just take care about the constraints when you declare the array for each test case separately. Works fine here 