You qualify for the exclusion now (residing in it 2 of the last 5 years), But you will get a prorata share of the exclusion either way. The one year you rented it will be subject to cap gains (in addition to one of depreciation recapture) under the Qualified Use I believe it is called. Example: rented for one year, resided in for 2 years, 1/3 of gain is not exempt; lived in it for 3 years, rented for 1 year, 1/4 of gain is not exempt.
This is because you rented it Prior to meeting the 2 years as your residence.
make an appointment with a CPA. I believe sec 121 exclusion is 2 years of the the last 5yrs used as personal residence, but confirm that with a tax pro.