PayPal Software Engineer interview questions

On-campus placements. The first round consisted of MCQs related to aptitude and computer science. The students who were shortlisted had two more rounds of technical interviews. Most of the interview questions were on data structures. Code had to be written on paper with proper explanation of the algorithm used. In-depth knowledge of the projects done is a must.

From various interviewers on-site, I was asked: - Design and implement an iterator for a singly-linked list class. - How would you design a garbage collector? - Given two connected singly-linked lists (giving a T-shaped structure), find the node where they connect. - Implement a complete singly-linked list class in C++. - Cycle detection in singly-linked lists. - Describe the differences between C++ and Java. - Determine if a binary tree is balanced. - Describe the architecture of the systems of my current employer. - Describe how to maintain data integrity across concurrent reads/writes to/from a database. - How to remove duplicates from an array. - When does it make sense to store a tree ADT in an array? - How would you organize a data structure used for parsing arithmetic operations? (Like 3*2 + 4 = 10) - Write a python script to scan the files in a directory for a word. Return true if the word is found in at least one file and false if otherwise.