Microsoft Software Engineer interview questions

Given an char array. write a function that 'collapse' the array and send it back. e.g: for a given array 'abccdeefaassf' return abcdefasf' this can be done in O(n).

Round 1:- 3 coding questions covering queues , trees and other simple data structures Round 2:- 1) Print the boundary nodes in a tree in anticlockwise manner 2) Expansion of a string Technical interview:- Round 1:- Most things were asked from my resume. Then one coding question to "find the smallest non negative number which is not present in the array(unsorted) " Round 2:- He asked tell me about yourself. Then asked to write code to add two polynomials. Next round was HR round....sadly i was not selected for HR.