7 Important Data Structures and Algorithms for Coding Interviews

Most candidates nowadays try to memorize the hundreds of coding interview questions available on the internet in order to grasp the interview. However, this strategy of retaining questions does not always work. Since if you do not understand the principles of programming, such as data structures and algorithms, the interviewers’ simplest to simplest questions might give you a headache.

The most dangerous weapon that the interviewer has in order to test your programming knowledge are the basic data structures and algorithms that we all seem to ignore because we believe they are not useful in our coding part, but the truth is quite the opposite as these data structures form the foundation of every high order data structure that we use or algorithms that we follow. Let’s look at the top 7 data structures and algorithms you need to understand in order to ace your coding interview.

1. Hash tables

hash tables
Hash Table

The hashing element of the data structure is undoubtedly the most significant  data structure that the interviewer will inquire about because it allows us to  save one of the most valuable coding resources, namely time. 

The hash table is the most common question asked by interviewers since it can  be utilized with any data structure or algorithm and is mostly used for  algorithm optimization. Hash tables allow us to store data in data structures  while performing operations such as read, write, and modify in O (1) time. It  calculates the corresponding index of the supplied value in the specified array  using a hash function.

Another reason is that it has a wide range of applications, including: 

  • Sets data structure in python 
  • Caches 
  • Database indexing 
  • Associative arrays 

2. Array

7 Important Data Structures and Algorithms for Coding Interviews

The array is another favorite data structure of interviewers since it is  the foundation of every popular data structure. Stacks, queues, linked lists,  trees, and graphs are all implemented using the array data structure. 

The user can store numerous values of the same data type in neighboring memory places under the same name, and the values can be accessed easily  using the index of the values. The following are the most common array  applications: 

  • Sorting 
  • Matrix operations 
  • CPU scheduling 
  • Implementing stack, queue, heaps, hash tables etc. 

As a result of its role as the foundation of every data structure and algorithm,  the array has become one of the most popular data structures to be  questioned about in interviews. 

3. Sorting Algorithm

Merge Sorting Algorithm

Because most algorithms perform best on sorted data, sorting  becomes the foundation of practically all algorithmic tactics. As it measures  your problem-solving ability and basic knowledge, it is the most basic algorithm  found in any interview. 

You must be familiar with a variety of sorting algorithms, some of which are  listed below: 

  • Bubble sort 
  • Selection sort 
  • Merge sort 
  • Heap sort 
  • Insertion sort 
  • Quick sort (Most used)

Along with the sorting algorithms and their time complexities you must be also  aware about the kind of sorting technique you can use for a particular  problem as it has many applications like entry matching, searching etc. 

4. Recursion

7 Important Data Structures and Algorithms for Coding Interviews
Merge Sort Recursion

It’s also a frequently asked question, and I can almost guarantee  that you’ll be asked at least one question about the recursion function and how  to use it. Most firms will not question you directly about recursion, but they will  always give you a recursive problem to solve

A recursive function is one that calls itself until it reaches the base condition.  For tasks that must be separated into subparts, such as divide and conquer, a  recursive function can be used instead of an iterative approach. Among the  recursive problems are: 

  • Factorial 
  • Fibonacci series (Most asked) 
  • Tower of Hanoi 
  • Tree traversals etc. 

You must be familiar with all these recursive problems along with their time  complexities and recursive function algorithm for the same for grasping more  rise in your interview score. 

5. Graphs and Trees

Graphs and Tree

Graphs and trees are two of the most significant data  structures to be familiar with in order to do well in interviews. The two most  basic things you must understand are how these two data structures are built using nodes and edges, and how they are navigated. 

The questions on graph and tree are not directly addressed, but you will be  given a circumstance such as you must traverse a matrix as a tree or graph. Pre-order, in-order, and post-order traversals, as well as graph traversals like  depth first search and breadth first search, must all be familiar to you. 

You must also be aware of different implementations of tree and graph such as: 

  • Finding shortest path 
  • Gaming 
  • Google maps 
  • Facebook etc.

6. Shortest path Algorithms

7 Important Data Structures and Algorithms for Coding Interviews
Shortest Path Algorithm

Finding the shortest path between two or more nodes in a graph is known as a shortest path issue. The main reason why this  question is frequently asked by interviewers is because it has a wide range of  real-life applications, which are stated below: 

  • To find the smallest possible route from one place to another place.
  • Helps in finding a route between two physical links within a given bound of time.
  • To solve problems like Rubik’s Cube where we can derive minimum  number of moves required for solving the cube. 
  • It is the backbone of Google Maps direction feature. 

You must be aware of some of the basic shortest path algorithms such as  Dijkstra algorithm, Bellman-Ford algorithm, Floyd-War shall algorithm etc. and how these algorithms can be used in practical scenarios

7. Stack and Queue

Stack and Queue
Stack Vs Queue

Speed is one of the most essential elements that a  programmer should consider when programming and which is the primary reason Stack and Queue are used. As applicants are frequently confused  between these data structures and their implementations, it becomes a major interview question. 

In order to ace the interview, you should be familiar with the following operations: 

  • Must know the basic differences between Stack and Queue.
  • The Basic meanings of LIFO and FIFO and how they differ.
  • Basic stack operations like push, pop, peep etc. 
  • Basic queue operations like enqueue, dequeue. 

Along with the above listed things, you must also know the basic problems solved using stack and queue like Undo command, Depth first search, Breadth  first search, CPU scheduling, disk scheduling, expression evaluation,  parenthesis matching etc. 


Rather than buying a book with a thousand interview questions, the best way to  prepare for your interview is to comprehend the fundamentals of the topic. If you think about the data structures and algorithms discussed above, you’ll surely ace your coding interview and start a successful career.

Did you find these important Data Structures and Algorithms for Coding Interview helpful? Tell us in the comment section below.

Happy Coding!!

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