# Algorithms Data Structures Interview Questions

### Why Did You Opt for a Career in Software Development?

One way to answer this question is to explain how you first got interested in software and describe some of the first programs you wrote. Then talk about some of the personal projects or open source contributions you’ve made to illustrate your interest in the field.

### Are Linked Lists Considered Linear or Non-Linear Data Structures?

Linked lists are linear data structures.

### Explain Stack Along With Its Applications.

A stack is a data structure in which elements are placed one on top of the other and additions and deletions can occur only at the top. Stacks can be used in the following applications:

• A stack can be used in applications where users are enabled to backtrack on previous operations by one step or move forward with a new operation.
• Converting infix expressions into postfix expressions.
• The process of reversing the characters in a string can be completed by placing them in a stack and using the pop operation.
• A postfix expression is a format for arranging operators and operands in which the operators are always placed after the operands. The following is an example of a postfix expression:

The infix version of this expression is:

### What Is a Binary Search Tree?

A binary search tree is a special tree implementation in which internal nodes store keys greater than the keys in the left subtrees and less than the keys in the right subtrees.

### Define an Asymptotic Analysis of an Algorithm.

An asymptotic analysis determines the mathematical run-time performance of different algorithms. Through asymptotic analysis, we are able to establish the best case, worst case, and average case scenarios for algorithms.

The following notations are used in the asymptotic analysis of algorithms.

The big oh notation, O(n), describes the upper bound for the runtime of an algorithm. It thus describes the worst case time complexity of an algorithm.

This is the lower bound, or the best case scenario, for an algorithm’s running time.

The theta notation combines both the upper and lower bound running time of an algorithm.

### Are Dictionaries or Lists Faster for Lookups?

This question tests your grasp of the implications for Python data structures and the algorithms you can implement on top of them. Lists are slower for lookups: it’ll take O(N) time since filtering through for a value will require as a worst-case scenario filtering through every value in the list. Dictionaries are well-set up with key-value pairs, similar to a hash table. Thus the time to search will be O(1) as long as you have the correct key.

### What Is the Most Challenging Project You Encountered on Your Learning Journey?

Be honest when answering this question. Start by describing the project and what you were trying to achieve. Then describe the challenges you faced and your gaps in learning. Finish by explaining how you filled those gaps and completed the project.

### What Is the For-In Loop in JavaScript? Give Its Synta

The for-in loop is a fundamental part of iterating through data structures. You should be able to describe its syntax to interviewers without hesitation. This is the case for-in loop implementation in JavaScript. You would loop through an array by replacing the object name with the array name, and then place the piece of iterative code inside the block.

Arrow functions are a concise and short way to write functions in ES6 and above. They are a way for you to condense your algorithmic logic. The following example describes an arrow function which simply prints “hello” in the JavaScript console. 