Microsoft Software Development Engineer In Test (SDET) interview questions

on site interview, first round question: given two arrays(int), they have common numbers, output an array, which contains common numbers, with duplicate numbers, for example, a1={1,1,1,2,-8,9} a2={1,1,-8,10} output: a={1,1,-8} time complexity requirement: O(n)

on-site interview, flew to hq. interviewed with 5 people about 1 hour each