Opower interview question

Phone technical round was done using collabedit to do some programming questions. 1. FizzBuzz program 2. For an array of numbers, count how many times a number appears in an array . print as -><number> : <count> (answer: Solve using hashmap, more efficient) What is the bigO for this? (answer: 1) 3. How would you process a huge amount of data in parallel? (answer: MapReduce) 4. Print all primes from 2 to 1000