Is it okay to do cardio and strength training on the same day?

I'm trying to get my body lookin' good in a short amount of time. So, I'm eating healthy, cutting calories, and exercising more. When I do cardio I typically run for about 20-30 mins then fast walk for 20 mins. I also like to do pilates for about 30-40 mins to target my butt, abs, obliques, and legs. I've done them both on the same day and I feel good afterwards, just exhausted. I'm trying to do at least the cardio everyday and pilates every other day. Is it okay to do both on the same day? Or should I alternate cardio one day, pilates the next...