Pregunta de entrevista de Google

First interview: 1. Serialize BST Second interview: 1. eliminate duplicate element in an array (maybe using hash table and explain it) 2. design a uniform random function for countries name according to their population such as country = {A, B} and population = { 10K, 20K}, the random function should generate either A or B and the number of B should be two times larger than the number of A