# Data structure Interview Questions

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### Software Engineer at Facebook

Apr 24, 2011
 “Print a singly-linked list backwards, in constant space and linear time.”

### Software Development Engineer at Amazon.com

Feb 27, 2010
 “Implement a function to validate whether a given binary tree is a BST (i.e. write an isBST() function).”

### Software Engineer at Facebook

Apr 24, 2011
 “Convert a binary search tree to a sorted, circular, doubly-linked list, in place (using the tree nodes as the new list nodes).”

### Software Design Engineer at Amazon.com

Mar 19, 2009
 “Given a string find the first non-repeated character.”

### Data Scientist Intern at LinkedIn

Feb 25, 2012
 “Find the second largest element in a Binary Search Tree”

### Software Engineer at Google

Mar 21, 2010
 “You have a genealogy: 1) Describe a data structure to represent it. 2) Given any two people within the genealogy, describe an algorithm to determine if they share a common ancestor. You just need...”

### Software Development Engineering Intern at Amazon.com

Jun 23, 2012
 “You are given an array with n positive integers where all values in the array are repeated except for one. Return the one that is not repeated.”

### Financial Software Developer at Bloomberg L.P.

Dec 8, 2012
 “Given 10 cups to locate the bottle poisoned wine from a batch of normal ones, you can make any mixture of them and test your mixtures by mouses. However the density of poison in the mixture, the...”

### Software Engineer/Developer for Microsoft Windows Azure Fabirc Foundations Group at Microsoft

May 9, 2011
 “Assume that you are given the head and tail pointers of a doubly linked list where each node can also have a single child pointer to another similar doubly linked list. There are no cycles in this...”

### Software Developer at Epic Systems Corporation

Aug 29, 2009
 “I have a log that consists of more than 100 million lines. Each line is just a data about user login, login time, etc. I want to sort them based on user login, and then if there is a tie based on...”
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