DS-and-ML-interview-questions.ipynb

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    "[Source](http://houseofbots.com/news-detail/3632-4-data-science-and-machine-learning-interview-questions-for-it-professionals)\n"
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   "source": [
    "# Data Science and Machine Learning Interview Questions For IT Professionals"
   ]
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   "source": [
    "\n",
    "The data structure, algorithms, string, array are a core part of any Programming Language job interview. It doesn't matter whether you are a C++ developer, a Java developer or a Web developer working in JavaScript, Angular, React, or Query. \n",
    "\n",
    "There are a lot of computer science graduates and programmers applying for programming, coding, and software development roles at startups like Uber and Netflix; big organizations like Amazon, Microsoft, and Google; and service-based companies like Infosys or Luxsoft, but many of them have no idea of what kind of programming interview questions to expect when you're applying for a job with these companies.\n",
    "\n",
    "In this article, I'll share some frequently asked programming interview questions from different interviews for programmers at different levels of experience, from people who have just graduated from college to programmers with one to two years of experience.\n",
    "\n",
    "As a computer science graduate, its expected from a programmer to have strong knowledge of both basic data structures e.g. array, linked list, binary tree, hash table, stack, queue and advanced data structures like the binary heap, trie, self-balanced tree, circular buffer etc. I have taken a lot of Java interviews for both junior and senior positions in the past, and I have been also involved in interviewing C++ developer. One difference which I have clearly noticed between a C++ and a Java developer is their understanding and command of Data structure and algorithms.\n",
    "\n",
    "On average, a C or C++ developer showed a better understanding and application of data structure and their coding skill was also better than Java developers. This is not a coincidence though. As per my experience, there is a direct correlation between a programmer having a good command of the algorithm also happens to be a good developer and coder.\n",
    "\n",
    "I firmly believe that interview teaches you a lot in very short time and that's why I am sharing some frequently asked Data structure and algorithm questions from various Java interviews.\n",
    "\n",
    "If you are familiar with them than try to solve them by hand and if you do not then learn about them first, and then solve them. If you need to refresh your knowledge of data structure and algorithms then you can also take help from a good book our course like Data Structures and Algorithms: Deep Dive Using Java for quick reference."
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    "Let's dive in:\n",
    "\n",
    "1. What's the trade-off between bias and variance?  \n",
    "\n",
    "2. What is gradient descent?  \n",
    "\n",
    "3. Explain over- and under-fitting and how to combat them?  \n",
    "\n",
    "4. How do you combat the curse of dimensionality?  \n",
    "\n",
    "5. What is regularization, why do we use it, and give some examples of common methods?  \n",
    "\n",
    "6. Explain Principal Component Analysis (PCA)?  \n",
    "\n",
    "7. Why is ReLU better and more often used than Sigmoid in Neural Networks?  "
   ]
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    "- **What is data normalization and why do we need it?** I felt this one would be important to highlight. Data normalization is very important preprocessing step, used to rescale values to fit in a specific range to assure better convergence during backpropagation. In general, it boils down to subtracting the mean of each data point and dividing by its standard deviation. If we don't do this then some of the features (those with high magnitude) will be weighted more in the cost function (if a higher-magnitude feature changes by 1%, then that change is pretty big, but for smaller features, it's quite insignificant). The data normalization makes all features weighted equally.  \n",
    "\n",
    "- **Explain dimensionality reduction, where it's used, and it benefits?** Dimensionality reduction is the process of reducing the number of feature variables under consideration by obtaining a set of principal variables which are basically the important features. Importance of a feature depends on how much the feature variable contributes to the information representative of the data and depends on which technique you decide to use. Deciding which technique to use comes down to trial-and-error and preference. It's common to start with a linear technique and move to non-linear techniques when results suggest inadequate fit. Benefits of dimensionality reduction for a data set may be: (1) Reduce the storage space needed (2) Speed up computation (for example in machine learning algorithms), fewer dimensions mean less computing, also less dimensions can allow usage of algorithms unfit for a large number of dimensions (3) Remove redundant features, for example no point in storing a terrain's size in both sq meters and sq miles (maybe data gathering was flawed) (4) Reducing a data's dimension to 2D or 3D may allow us to plot and visualize it, maybe observe patterns, give us insights (5) Too many features or too complex a model can lead to overfitting.  \n",
    "\n",
    "- **How do you handle missing or corrupted data in a dataset?** You could find missing/corrupted data in a dataset and either drop those rows or columns or decide to replace them with another value. In Pandas, there are two very useful methods: IsNull() and drop() that will help you find columns of data with missing or corrupted data and drop those values. If you want to fill the invalid values with a placeholder value (for example, 0), you could use the fill() method.\n",
    "\n",
    "\n",
    "* How would you go about doing an Exploratory Data Analysis (EDA)? The goal of an EDA is to gather some insights from the data before applying your predictive model i.e gain some information. Basically, you want to do your EDA in a coarse to fine manner. We start by gaining some high-level global insights. Check out some imbalanced classes. Look at the mean and variance of each class. Check out the first few rows to see what it's all about. Run a pandas df.info() to see which features are continuous, categorical, their type (int, float, string). Next, drop unnecessary columns that won't be useful in analysis and prediction. These can simply be columns that look useless, ones where many rows have the same value (i.e it doesn't give us much information), or it's missing a lot of values. We can also fill in missing values with the most common value in that column, or the median. Now we can start making some basic visualizations. Start with high-level stuff. Do some bar plots for features that are categorical and have a small number of groups. Bar plots of the final classes. Look at the most \"general features\". Create some visualizations about these individual features to try and gain some basic insights. Now we can start to get more specific. Create visualizations between features, two or three at a time. How are features related to each other? You can also do a PCA to see which features contain the most information. Group some features together as well to see their relationships. For example, what happens to the classes when A = 0 and B = 0? How about A = 1 and B = 0? Compare different features. For example, if feature A can be either \"Female\" or \"Male\" then we can plot feature A against which cabin they stayed in to see if Males and Females stay in different cabins. Beyond the bar, scatter, and other basic plots, we can do a PDF/CDF, overlayed plots, etc. Look at some statistics like distribution, p-value, etc. Finally, it's time to build the ML model. Start with easier stuff like Naive Bayes and Linear Regression. If you see that those sucks or the data is highly non-linear, go with polynomial regression, decision trees, or SVMs. The features can be selected based on their importance from the EDA. If you have lots of data you can use a Neural Network. Check ROC curve. Precision, Recall  \n",
    "* How do you know which Machine Learning model you should use? While one should always keep the \"no free lunch theorem\" in mind, there are some general guidelines. I wrote an article on how to select the proper regression model here. This [cheat shee][1]t is also fantastic!  \n",
    "* Why do we use convolutions for images rather than just FC layers? This one was pretty interesting since it's not something companies usually ask. As you would expect, I got this question from a company focused on Computer Vision. This answer has 2 parts to it. Firstly, convolutions preserve, encode, and actually use the spatial information from the image. If we used only FC layers we would have no relative spatial information. Secondly, Convolutional Neural Networks (CNNs) have a partially built-in translation in-variance, since each convolution kernel acts as it's own filter/feature detector.  \n",
    "* What makes CNN's translation invariant? As explained above, each convolution kernel acts as it's own filter/feature detector. So let's say you're doing object detection, it doesn't matter where in the image the object is since we're going to apply the convolution in a sliding window fashion across the entire image anyways.  \n",
    "* Why do we have max-pooling in classification CNNs? Again as you would expect this is for a role in Computer Vision. Max-pooling in a CNN allows you to reduce computation since your feature maps are smaller after the pooling. You don't lose too much semantic information since you're taking the maximum activation. There's also a theory that max-pooling contributes a bit too giving CNN's more translation invariance. Check out this great video from Andrew Ng on the [benefits of max-pooling][2].  \n",
    "* Why do segmentation CNNs typically have an encoder-decoder style/structure? The encoder CNN can basically be thought of as a feature extraction network, while the decoder uses that information to predict the image segments by \"decoding\" the features and upscaling to the original image size.  \n",
    "* What is the significance of Residual Networks? The main thing that residual connections did was allow for direct feature access from previous layers. This makes information propagation throughout the network much easier. One very interesting[ paper][3] about this shows how using local skip connections gives the network a type of ensemble multi-path structure, giving features multiple paths to propagate throughout the network.  \n",
    "* What is batch normalization and why does it work? Training Deep Neural Networks is complicated by the fact that the distribution of each layer's inputs changes during training, as the parameters of the previous layers change. The idea is then to normalize the inputs of each layer in such a way that they have a mean output activation of zero and standard deviation of one. This is done for each individual mini-batch at each layer i.e compute the mean and variance of that mini-batch alone, then normalize. This is analogous to how the inputs to networks are standardized. How does this help? We know that normalizing the inputs to a network helps it learn. But a network is just a series of layers, where the output of one layer becomes the input to the next. That means we can think of any layer in a neural network as the first layer of a smaller subsequent network. Thought of as a series of neural networks feeding into each other, we normalize the output of one layer before applying the activation function and then feed it into the following layer (sub-network).  \n",
    "* How would you handle an imbalanced dataset? I have an article about this! Check out #3 :)  \n",
    "* Why would you use many small convolutional kernels such as 3x3 rather than a few large ones? This is very well explained in the [VGGNet paper][4]. There are 2 reasons: First, you can use several smaller kernels rather than few large ones to get the same receptive field and capture more spatial context, but with the smaller kernels you are using fewer parameters and computations. Secondly, because with smaller kernels you will be using more filters, you'll be able to use more activation functions and thus have a more discriminative mapping function being learned by your CNN.  \n",
    "* Do you have any other projects that would be related here? Here you'll really draw connections between your research and their business. Is there anything you did or any skills you learned that could possibly connect back to their business or the role you are applying for? It doesn't have to be 100% exact, just somehow related such that you can show that you will be able to directly add lots of value.  \n",
    "* Explain your current master's research? What worked? What didn't? Future directions? Same as the last question!  \n",
    "\n",
    "Conclusion\n",
    "\n",
    "There you have it! All of the interview questions I got when applying for roles in Data Science and Machine Learning. I hope you enjoyed this post and learned something new and useful!\n",
    "\n",
    "The article was originally published [here][5]\n",
    "\n",
    "Source: HOB\n",
    "\n",
    "[1]: https://www.google.com/search?tbs=simg:CAESqQIJvnrCwg_15JjManQILEKjU2AQaBAgUCAoMCxCwjKcIGmIKYAgDEijqAvQH8wfpB_1AH_1hL1B_1YH6QKOE6soyT-TJ9A0qCipKKoo0TS0NL0-GjA_15sJ-3A24wpvrDVRc8bM3x0nrW3Ctn6tFeYFLpV7ldtVRVDHO-s-8FnDFrpLKzC8gBAwLEI6u_1ggaCgoICAESBOmAAdwMCxCd7cEJGogBChsKCGRvY3VtZW502qWI9gMLCgkvbS8wMTVidjMKGAoGbnVtYmVy2qWI9gMKCggvbS8wNWZ3YgoXCgVtdXNpY9qliPYDCgoIL20vMDRybGYKGwoIcGFyYWxsZWzapYj2AwsKCS9tLzAzMHpmbgoZCgdwYXR0ZXJu2qWI9gMKCggvbS8waHdreQw&q=choose+ml+algorithm&tbm=isch&sa=X&ved=0ahUKEwi-js_8nNbaAhWB5YMKHUTLCEMQsw4INg&biw=1855&bih=990#imgrc=vnrCwg_5JjNUcM:\n",
    "[2]: https://www.coursera.org/learn/convolutional-neural-networks/lecture/hELHk/pooling-layers\n",
    "[3]: https://arxiv.org/abs/1605.06431\n",
    "[4]: https://arxiv.org/pdf/1409.1556.pdf\n",
    "[5]: https://towardsdatascience.com/data-science-and-machine-learning-interview-questions-3f6207cf040b\n",
    "\n",
    "  "
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    "\n",
    "[Source](http://houseofbots.com/news-detail/3640-4-100plus-programming-language-data-structure-algorithms-more-interview-questions-answers-for-programmers-part-1 \"Permalink to 100+ Data Structure, Algorithms & Programming Language Interview Questions Answers for Programmers\")\n",
    "\n",
    "# 100+ Data Structure, Algorithms & Programming Language Interview Questions Answers for Programmers\n",
    "\n",
    "### 100+ Data Structure, Algorithms & Programming Language Interview Questions Answers for Programmers - Part 1\n",
    "\n",
    "The data structure, algorithms, string, array are a core part of any Programming Language job interview. It doesn't matter whether you are a C++ developer, a Java developer or a Web developer working in JavaScript, Angular, React, or Query. \n",
    "\n",
    "There are a lot of computer science graduates and programmers applying for programming, coding, and software development roles at startups like Uber and Netflix; big organizations like Amazon, Microsoft, and Google; and service-based companies like Infosys or Luxsoft, but many of them have no idea of what kind of programming interview questions to expect when you're applying for a job with these companies.\n",
    "\n",
    "In this article, I'll share some frequently asked programming interview questions from different interviews for programmers at different levels of experience, from people who have just graduated from college to programmers with one to two years of experience.\n",
    "\n",
    "As a computer science graduate, its expected from a programmer to have strong knowledge of both basic data structures e.g. array, linked list, binary tree, hash table, stack, queue and advanced data structures like the binary heap, trie, self-balanced tree, circular buffer etc. I have taken a lot of Java interviews for both junior and senior positions in the past, and I have been also involved in interviewing C++ developer. One difference which I have clearly noticed between a C++ and a Java developer is their understanding and command of Data structure and algorithms.\n",
    "\n",
    "On average, a C or C++ developer showed a better understanding and application of data structure and their coding skill was also better than Java developers. This is not a coincidence though. As per my experience, there is a direct correlation between a programmer having a good command of the algorithm also happens to be a good developer and coder.\n",
    "\n",
    "I firmly believe that interview teaches you a lot in very short time and that's why I am sharing some frequently asked Data structure and algorithm questions from various Java interviews.\n",
    "\n",
    "If you are familiar with them than try to solve them by hand and if you do not then learn about them first, and then solve them. If you need to refresh your knowledge of data structure and algorithms then you can also take help from a good book our course like Data Structures and Algorithms: Deep Dive Using Java for quick reference.\n",
    "\n",
    "Data Structures, Algorithm and Programming Language Interview Questions\n",
    "\n",
    "For the sake of clarity and focus, I have categorized these data structure and algorithmic questions into various sub-category e.g. String questions, array-based questions, linked list questions, binary tree-related questions, searching and sorting based questions and bit manipulation questions.\n",
    "\n",
    "This way you can start with the topic you feel most comfortable and slowly progressing to the topic which you want to improve.\n",
    "\n",
    "1\\. String Interview Questions\n",
    "\n",
    "The string is probably the most used data structure. You will see it right from your programming course and you will use it throughout your professional project. There is hardly an application written in Java and C++ who doesn't use String.\n",
    "\n",
    "They are everywhere. From a C++ perspective, String is nothing but a null-terminated character array, but from Java perspective, String is a full-fledged object backed by character array.\n",
    "\n",
    "In this category, you will find questions which require String manipulations e.g. substring, reversing, searching, sorting, slicing and dicing etc.\n",
    "\n",
    "Here is a list of some of the frequently asked String Interview Questions from Coding Interviews:\n",
    "\n",
    "* Print duplicate characters from String? ([solution][1])  \n",
    "* Check if two Strings are anagrams of each other? ([solution][2])  \n",
    "* Print first non repeated character from String? ([solution][3])  \n",
    "* Reverse a given String using recursion? ([solution][4])  \n",
    "* Check if a String contains only digits? ([solution][5])  \n",
    "* Find duplicate characters in a String? ([solution][1])  \n",
    "* Count a number of vowels and consonants in a given String? ([solution][6])  \n",
    "* Count the occurrence of a given character in String? ([solution][7])  \n",
    "* Find all permutations of String? ([solution][8])  \n",
    "* Reverse words in a given sentence without using any library method? ([solution][9])  \n",
    "* Check if two String is a rotation of each other? (s[olution][10])  \n",
    "* Check if given String is Palindrome? ([solution][11])  \n",
    "\n",
    "If you can solve all these String questions without any help then you are in good shape. For more advanced questions, I suggest you solve problems given on [Algorithm Design Manual by Steven Skiena][12], a book with toughest algorithm questions.\n",
    "\n",
    "2\\. Array and Matrix Interview Questions\n",
    "\n",
    "Next to String is array, the second most frequently used data structure. Array stores element in a contiguous memory location and in C++ you can access array elements using pointer arithmetic as well, but in Java array is again an object, which provides just length method.\n",
    "\n",
    "You can only access the array using index and Java also doesn't valid index check and if you try to access an array with an invalid index, you will get java.lang.ArrayIndexOutOfBoundsException, so beware of that.\n",
    "\n",
    "Here is a list of some of the frequently asked Array and Matrix-based Programming questions:\n",
    "\n",
    "* Find a missing number in given integer array of 1 to 100? ([solution][13])  \n",
    "* Find the duplicate number on a given integer array? ([solution][14])  \n",
    "* Largest and smallest number in an unsorted integer array? (s[olution][15])  \n",
    "* Find all pairs of integer array whose sum is equal to a given number? ([solution][16])  \n",
    "* Find duplicate numbers in an array if it contains multiple duplicates? ([solution][17])  \n",
    "* Remove duplicates from given array in Java? ([solution][14])  \n",
    "* Sort an integer array in place using QuickSort algorithm? ([solution][18])  \n",
    "* Remove duplicates from an array in place? ([solution][14])  \n",
    "* Reverse an array in place in Java? ([solution][19])  \n",
    "* Find multiple missing numbers in given integer array with duplicates? ([solution][20])  \n",
    "* Perform a binary search in given array? ([solution][21])  \n",
    "* Transpose a Matrix? (s[olution][22])  \n",
    "* Add or subtract two Matrices? (s[olution][23])  \n",
    "* Multiply two Matrices in Java? ([solution][24])  \n",
    "* Calculate the average of all numbers in given array? ([solution][25])  \n",
    "\n",
    "If you need more advanced questions based upon array then you can see also seeThe Coding Interview Bootcamp: Algorithms + Data Structures,  a boot camp style course on algorithms, especially designed for interview preparation to get a job on technical giants like Google, Microsoft, Apple, Facebook etc.\n",
    "\n",
    "3\\. Linked List Interview Questions\n",
    "\n",
    "A linked list is another important data structure from interview point of view, here are some of the frequently asked linked list questions from programming interviews:\n",
    "\n",
    "Here is a list of some of the common linked list data structure questions from interviews:\n",
    "\n",
    "* Find the middle element of a singly linked list in one pass? ([solution][26])  \n",
    "* Find the 3rd node from the end in a singly linked list? ([solution][27])  \n",
    "* Check if a given linked list contains cycle? How to find the starting node of the cycle? ([solution][28])  \n",
    "* Find the length of a singly linked list? ([solution][29])  \n",
    "* Reverse a linked list? ([solution][30])  \n",
    "* Reverse a singly linked list without recursion? ([solution][31])  \n",
    "* Remove duplicate nodes in an unsorted linked list?  \n",
    "* Find the sum of two linked list using Stack? (p[rogram][32])  \n",
    "\n",
    "If you need more interview questions based upon linked list then you can also refer to this list of [30 linked list questions][33].\n",
    "\n",
    "4\\. Binary Tree Interview Questions\n",
    "\n",
    "tree data structure is another popular data structure in programming interviews. It has several variants e.g. binary tree, binary search tree and even binary heaps. It's almost guaranteed to see a couple of binary tree questions in programming job interviews.\n",
    "\n",
    "Here is a list of some of the popular binary tree interview questions from programming job interviews:\n",
    "\n",
    "* Implement a binary search tree?  ([solution][21])  \n",
    "* Pre-order traversal in given binary tree? ([solution][34])  \n",
    "* Traverse a given binary tree in Pre-order without recursion ([solution][35])  \n",
    "* Implement Post-order traversal algorithm? ([solution][36])  \n",
    "* Traverse a binary tree in Post order traversal without recursion ([solution][37])  \n",
    "* Print all leaves of a binary search tree? ([solution][38])  \n",
    "* Count a number of leaf nodes in the given binary tree? ([solution][39])  \n",
    "* In order traversal in given binary tree? ([solution][40])  \n",
    "* Print all nodes of given binary tree using inorder traversal without recursion ([solution][40])  \n",
    "* Check if a given binary tree is a binary search tree?   \n",
    "* Check if a binary tree is balanced or not?   \n",
    "* Given a binary search tree, how do you check whether there are two nodes in it whose sum equals a given value?   \n",
    "* convert a binary search tree to a sorted double-linked list.you are only allowed to change the target of pointers, but cannot create any new nodes.   \n",
    "* Given a binary search tree and a value k, How do you find a node in the binary search tree whose value is closest to k.  \n",
    "\n",
    "5\\. Stack and Queue Interview Questions\n",
    "\n",
    "Stack and Queue are derived data structure i.e. they are implemented either using an array or linked list, but they have unique features.\n",
    "\n",
    "A queue is also known as FIFO data structure, which means First In First Out i.e. the element which will be added first will also be retrieved first.\n",
    "\n",
    "Queue allows you to add an element at the tail and retrieve an element from the head, thus giving FIFO ordering.\n",
    "\n",
    "On the other hand, Stack is a LIFO data structure, Last In First out i.e. the element which will be added first will be the last one to go.\n",
    "\n",
    "This property is often used to convert a recursive algorithm into an iterative one. To learn more about Stack and Queue, I just you to join a good course on Data Structure and Algorithms e.g. Deep Dive into Data Structure in Java.\n",
    "\n",
    "For now, let's see some coding problems based on Stack and Queue data structure in Java.\n",
    "\n",
    "1. How do you implement a Queue using two Stacks?  \n",
    "\n",
    "2. Write a Java program to implement Stack using an array and linked list?   \n",
    "\n",
    "3. How do you implement Stack using Queues?  \n",
    "\n",
    "4. Given a binary tree, return the postorder traversal of its nodes' values, using Stack?  \n",
    "\n",
    "5. Difference between Stack and Queue data structure ([answer][41])\n",
    "\n",
    "If you need more such coding questions you can take help from books like [Cracking Code Interview][42], which presents 189+ Programming questions and solution. A good book to prepare for programming job interviews in a short time.\n",
    "\n",
    "6\\. Search and Sort Algorithmic Interview Questions\n",
    "\n",
    "Search and Sort based questions are the most popular algorithmic questions on any programming job interview. Interviewer often asks to implement various sorting algorithms e.g. Bubble sort, Quick sort, merge sort and asking to implement binary search etc.\n",
    "\n",
    "Other algorithms questions e.g. collision detection are not so popular but they are very interesting to solve and develop your grasp on creating your algorithms.\n",
    "\n",
    "* Implement the Bubble Sort algorithm? ([solution][43])  \n",
    "* Implement Iterative QuickSort Algorithm? ([solution][44])  \n",
    "* Implement the Bucket Sort Algorithm? ([solution][45])  \n",
    "* Implement Counting Sort Algorithm? ([solution][46])  \n",
    "* Implement the Insertion Sort Algorithm? ([solution][47])  \n",
    "* Implement a Merge Sort Algorithm? ([solution][48])  \n",
    "* Implement a Radix Sort Algorithm? ([solution][49])  \n",
    "* Implement Sieve of Eratosthenes Algorithm to find Prime numbers? ([solution][50])  \n",
    "* Find GCD of two numbers using Euclid's Algorithm? ([solution][51])  \n",
    "\n",
    "If you want to learn more about other algorithms, apart from search and sort e.g. advanced String algorithms then I suggest you check out the Data Structure and Algorithm MasterClass Part 1 - 2 on Pluarlsight.\n",
    "\n",
    "7\\. Bit Manipulation Interview Questions\n",
    "\n",
    "Last but not the least, we will see some bit manipulation based questions. There is a popular saying that, there are two kinds of programmers, one who knows binary and other's who don't.\n",
    "\n",
    "Yes, understand binary and playing with bits is an important skill for good programmers. Every major programming language e.g. Java and C++ provide both bitwise and bit shift operators, which you can use to manipulate bits and solve problems.\n",
    "* Check if a number is the power of two? ([solution][52])  \n",
    "* Check if a number is even or odd without using modulo operator? ([solution][53])  \n",
    "* Subtract two binary numbers? ([solution][54])  \n",
    "* Find the number of 1s (the Set bit) in a given Bit Sequence? ([solution][55])  \n",
    "\n",
    "8\\. Problem Solving Coding Questions\n",
    "\n",
    "So far we have seen most of the programming questions based upon data structure and algorithms but sometime you will also find questions from [software design][56], [Dynamic Programming][57], and other logical and [tricky ][58]questions.\n",
    "\n",
    "Here is a collection of some of those questions for your practice:\n",
    "\n",
    "* Swap two numbers without using the third variable? ([solution][59])  \n",
    "* Check if two rectangles overlap with each other? ([solution)][60]  \n",
    "* Design a Vending Machine? ([solution][61])  \n",
    "* Implement an LRU Cache in your favorite programming language? ([solution][62])  \n",
    "* Check if a given number is a Palindrome? ([solution][63])  \n",
    "* Check if a given number is an Armstrong number? ([solution][64])  \n",
    "* Find all prime factors of a given number? ([solution][65])  \n",
    "* Check if a given number is a positive or negative in Java? ([solution][66])  \n",
    "* Find the largest prime factor of a given integral number? ([solution][67])  \n",
    "* Print all prime numbers up to a given number? ([solution][68])  \n",
    "* Print Floyd's triangle? ([solution][69])  \n",
    "* Print Pascal's triangle? ([solution][70])  \n",
    "* Calculate the square root of a given number? ([solution][71])  \n",
    "* Check if given number is a prime number? ([solution][72])  \n",
    "* Add two numbers without using plus operator in Java? ([solution][73])  \n",
    "* Check if a given number is even/odd without using Arithmetic operator? ([solution][74])  \n",
    "* Print a given Pyramid structure? ([solution][75])  \n",
    "* Find the highest repeating world from a given file in Java? ([solution)][76]  \n",
    "* The reverse is given Integer in Java? ([solution][77])  \n",
    "* Convert a decimal number to binary in Java? ([solution][78])  \n",
    "* Check if a given year is a leap year in Java? ([solution][79])  \n",
    "\n",
    "That's all about some data structure and algorithm interview questions for programmers. Remember, its one of the most important topic for all levels of programmers, but its even more important for freshers, computer science graduates and junior programmers with 1 to 2 years of experience.\n",
    "\n",
    "As you get more experienced, you started seeing less number of data structure and algorithm questions e.g. a Java developer with 3 to 4 years of experience will see the lot less DS and also questions then freshers and a more senior Java developer e.g. someone with 5 to 6 years of experience will see even less.\n",
    "\n",
    "Nonetheless, its an important topic and programmer should not overlook it. I have found good companies like Google, Microsoft, Amazon they use Data structure and algorithm questions all the times.\n",
    "\n",
    "On the algorithmic front, there are more e.g. interview questions based on Dynamic Programming and backtracking, which I have not shared here, but I'll add it sometime later. If you come across any good data structure and algorithm question, don't feel shy to share with us.\n",
    "\n",
    "Thanks a lot for reading this article so far. If you like these Data Structure and Algorithm  Interview questions then please share with your friends and colleagues. If you have any questions or feedback then please drop a note.\n",
    "\n",
    "Source: HOB\n",
    "\n",
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    "[23]: http://www.java67.com/2016/10/how-to-add-and-subtract-two-matrices-in-java.html\n",
    "[24]: http://www.java67.com/2016/10/how-to-multiply-two-matrices-in-java.html\n",
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    "[79]: http://www.java67.com/2012/12/how-to-check-leap-year-in-java-program.html\n",
    "\n",
    "  "
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