Amazon Software Developer interview questions

Got scheduled an interviews which consisted of 3 phone calls after my friend dropped my resume off to Amazon (he works there). Some questions were hard, some were not, they all consisted of things you learn in University level Computer Science courses; reduce time complexity and memory complexity, that's what they were looking for. Some questions caught me off guard but they are all answerable if you study. Here were the questions: 1st interview: Given an array of integers, return in a function the number of instances odd numbers Given a binary tree, return the minimum depth of a particular leaf node 2nd Interview: Given an integer, write a function which return whether or not the integer is divisible by 2 Given a function which takes in a 2D point "n" , an array of 2D points and a number "k", return the k closest-points to "n" 3rd Interview: Given a singly-linked list, return the 3rd from last element