Hello Himanshu.
First of all, hope you filled the hostel admission form(if not then you can go through the following link).
http://allduniv.ac.in/old/images/facilities/hostel/hostel_admission_form.pdf
Hostels are available in campus of University of Allahabad for girls and separate for boys. There are 3-4 buildings of hostels. Sharing of room depends on which building you’re choosing. Rooms of dual sharing are available and are spacious.  For international students there’s separate hostel which is provided to them. Mess- Food - average Cost - average PGs- PGs are available at normal prices in all over the city, the ones near university are a bit expensive than the other parts of the city. Rent amount: Around 4000-6000 per month.
Hostels in AU are alloted purely on the basis of merit of UGAT/PGAT entrance. The Hostels will be available from the July month onwards. As you belong to General Category(as you did not mention any other) and with 155 marks, it is very difficult for you to get hostel as your marks are not that high.

However, always hope for the best! Wish you luck.