Friday, August 2, 2024

# Grokking The Dynamic Programming Interview

## What Are Some Characteristics Of Dynamic Programming

Top 5 Dynamic Programming Patterns for Coding Interviews – For Beginners

The problem can be divided into stages with optimal policies for each stage.

The variable states in each stage of the process examine how future actions will be influenced by present decisions.

In dynamic programming, you develop a recursive optimizationprocedure to build a solution to the N-stage problem.

We use the dynamic programming approach when there are problems that can be broken down into sub-problems.

Thus in dynamic programming, the results can be reused.

And by learning common algorithms, youll be able to navigate programming problems and solutions using dynamic programming for coding interviews.

Now lets dig into this course.

Want to know more about the Grokking series on Educative?

In this pattern youll work on this and other special cases of knapsacks such as:

Equal Subset Sum Partition

Subset Sum

Example challenge of subset sum: Given a set of positive numbers, determine if a subset exists whose sum is equal to a given number S.

Minimum Subset Sum Difference

Count of Subset Sum

Target Sum

Example challenge of a target sum: Given a set of positive numbers and a target sum S. Each number should be assigned either a + or – sign. Then find out total ways to assign symbols to make the sum of numbers equal to target S.

## Who Are The Authors Of This Course

This course was developed by Design Gurus, a group of senior engineers and hiring managers whove been working at , Google, Amazon, and Microsoft. The authors of this course have a lot of experience in conducting coding and system design interviews and know exactly what is being asked in these interviews. Other courses developed by the same team can be found on their website.

Lets evaluate different aspects of this course.

## Take Ownership Of Your Education

Big Tech interviews are both fairly standard and widely documented. There is a wealth of resources to prepare for the coding interview and a growing pile of systems design resources.

Itâs easy to get lost in so much information: which is why you should make a plan on how you will get âinterview-readyâ.

Create a study plan with topics you want to cover for the interview types youâre expecting to have. Learn the theory, then practice this with practice and exercises where you create something from scratch: implementing a data structure, drawing up a diagram.

There is no shortage of people complaining about the difficult interview process Big Tech has. However, I know of no other industry where you can get a high-paying job with no college degree, no connections: purely through interviews that are fairly standard among the highest paying employers like Netflix, Airbnb, Uber, Facebook, Pinterest, and others.

Tech interviews being âstandardâ across the Big Tech makes preparing for these a high-leverage activity: study once, interview many times. Once you prepare, just make sure your software engineering resume grabs the attention of the recruiters.

Good luck â and if you are looking for more advice for senior and above interviews, I have some.

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Also Check: Aws Solution Architect Associate Interview Questions

## The Brute Force Solution:

A basic brute force solution could be to try all combinations of the given items to choose the one with maximum profit and a weight that doesnt exceed C. Heres what our algorithm will look like:

for each item i

create a new set which includes one quantity of item i if it does not exceed the capacity, and

recursively call to process all items

create a new set without item i, and recursively process the remaining items

return the set from the above two sets with higher profit

The only difference between the 0/1 Knapsack optimization problem and this one is that, after including the item, we recursively call to process all the items . In 0/1 Knapsack, we recursively call to process the remaining items.

Heres the code:

`public class Knapsack private int knapsackRecursive public static void main  int weights =  int maxProfit = ks.solveKnapsack System.out.println }}`

The time and space complexity of the above algorithm is exponential O, where n represents the total number of items.

Theres a better solution!

## How To Handle The Unstructured Nature Of Leetcode

If you are seeking a new job or preparing for a coding interview, you will definitely know LeetCode. It is probably the largest online repository of coding interview questions and also contains a vibrant community to discuss algorithms with other fellow engineers. One of the biggest challenges with LeetCode is that it lacks organization it has a huge set of coding problems, and one feels lost on where to begin or what to focus on.

To make the coding interview preparation process organized, this course breaks coding questions into problem-solving patterns like Sliding Window, Fast & Slow Pointers, Two Heaps, Topological Sort, etc. Following this patterns-based approach helps people to map a new problem to an already known problem. The idea behind these patterns is that once youre familiar with a pattern, youll be able to solve dozens of problems with it.

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## S To Solve A Coding Problem Using Recursion

Once you have identified that a coding problem can be solved using Recursion, You are just two steps away from writing a recursive function.

1. Find the base case2. Finding how to call the method and what to do with the return value.

As discussed above, finding a base case for any recursive solution is the first step toward writing a recursive function in Java or any other programming language. This is usually the simplest way to solve the problem without using recursion.

For example, when you calculate factorial, the base case is factorial which is 1, you mean you know the answer so you can directly return it and from there onwards recursion will unroll and calculate factorial for the given number.

Once you have done that, you need to find a way to call the recursive method and what to do with the result returned by the method, sometime you may need to add, multiply, and divide those depending upon your problem. This will be more clear when you will solve Recursive Practice Questions in Java.

And, if you want to learn Recursion from scratch then Recursion for Coding Interviews in Java course on Educative is a great resource to start with, I really loved it as it also forms the basis for Dynamic Programming which they have explained in their Grokking Dynamic Programming Patterns for Coding Interview course.

## My Favorite Educative Courses For Coding Interviews And Software Development In 2022

Without wasting any more of your time, here is a list of the best interactive, text-based courses from Educative for programmers and software engineers.

These interactive text-based courses have been created by experts and Educatives state-of-the-art platform that makes learning easy with interactive quizzes, and the ability to run the program right from your browser.

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## Determine The Base Case

Now that we have our recurrence relation, we need to figure out our base case. All recursive functions must have at least one base case, otherwise we will get stuck in an infinite recursion. How do we identify base cases? This is also something that comes with practice, but there are some different ideas that we can consider when confronted with this task.

One type of base case is to stop recursing for an input that exists at the edge of the possible range of inputs. For example, if we have a parameter that can be any integer 0, we might have a base case for when that integer is 0. This is what we did in our Fibonacci example, except we also had a base case for n = 1, since we call fib within the function and fib is outside the range of possible values for n.

Another type of base case is to stop recursing when we hit an invalid input. A good example of this is depth first search on a binary tree:

`functiondfs`

Here, we just return false if we encounter a null node, since theres no way for a subtree that doesnt exist to contain the value were looking for.

For our house robber problem, we already discussed a couple possible base cases when we were trying to figure out the recurrence relation:

• What do we do if we have one house? Obviously we rob that one!
• What do we do if we have two houses? Obviously we pick the one with more money!
`f=hf=maxf=max,f)`

## Dynamic Programming Predictable And Preparable

GROKKING the CODING INTERVIEW review || Best FAANG interview prep?

One of the reasons why I personally believe that DP questions might not be the best way to test engineering ability is that theyre predictable and easy to pattern match. They allow us to filter much more for preparedness as opposed to engineering ability.

These questions typically seem pretty complex on the outside, and might give you an impression that a person who solves them is very good at algorithms. Similarly, people who may not be able to get over some mind-twisting concepts of DP might seem pretty weak in their knowledge of algorithms.

The reality is different, and the biggest factor in their performance is preparedness. So lets make sure everyone is prepared for it. Once and for all.

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## Grokking The Coding Interview By Educativeio Is Arguably One Of The Best Overall Coding Interview Prep Resources

Thats because the creators of this course had one goal in mind for programmers: the ability to map a new problem to an already known problem.

So instead of 25, 50 or even 100 coding problems, youll find 16 patterns for solving coding questions.

The idea is that once youre familiar with a pattern, youll be able to solve multiple problems with it.

This course is arguably Educative.ios best release. Find out more in our comprehensive Grokking the Coding Interview review.

#### Course Layout

Educative.io has an interactive layout. So instead of setting up your own environment, youll do all work inside the same browser using over 1000 coding playgrounds.

In this courses interactive coding playground, you can solve problems in Java, Python 3, JavaScript or C++.

Educative.io

Each of the 16 patterns in Grokking the Coding Interview is given its own module. Some of the patterns include:

Price: \$39 per month / \$279 per year for full platform access Duration: 19.5 hours Format: Video Certificate: Yes

Zero to Mastery

## What Our Learners Are Saying

I really love the course. It’s one place where all the important DP problems with good explanations are present. The course gave me confidence in thinking and solving DP problems. The course preview chapters had such a good explanation that I went forward and bought it.

Amit Gupta

Software Engineer

This course has easy to understand explanations of all the famous DP problems. It helped me overcome my fears to handle a DP problem in the interview.

David Huang

Sr. Software Engineer

I’m so happy to take this course, it helped me think about DP problems. Thank you guys.

Sanket Mehta

Software Engineer

This course has literally taken away the fear of DP from my life and feel so much more confident going in. This course is life saver and changer. Thank you so much.

Rahul Kumar

Software Engineer

I really love the course. It’s one place where all the important DP problems with good explanations are present. The course gave me confidence in thinking and solving DP problems. The course preview chapters had such a good explanation that I went forward and bought it.

Amit Gupta

Software Engineer

This course has easy to understand explanations of all the famous DP problems. It helped me overcome my fears to handle a DP problem in the interview.

David Huang

Sr. Software Engineer

I’m so happy to take this course, it helped me think about DP problems. Thank you guys.

Sanket Mehta

Read Also: Do’s And Don Ts Of Interview

## Pattern : Palindromic Subsequence

Palindromic Subsequence is the sequence of characters within a string that reads the same forwards and backwards.

So for example the longest palindromic subsequence in ABDBCA would be ABDBA.

Longest Palindromic Sequence

Longest Palindromic Substring

Example challenge of longest palindromic substring: Given a string, find the length of its Longest Palindromic Substring .

Count of Palindromic Substrings

Minimum Deletions in a String to make it a Palindrome

Palindromic Partitioning

## Engineers Love Learning With Educative

Onboarding plans in Educative has significantly streamlined our onboarding process. Giving new hires a checklist of classes and tasks makes it very convenient.â

âEngineering Manager at Bread

âA rich yet very easy-to-use platform. A wonderful team and a true opportunity to make a difference by sharing my skills â couldnât have asked for better!â

âSamia Khalid, Senior AI Engineer at Microsoft

âAn interactive and in-browser embedded coding environment, thatâs just perfect. I believe this to be a very effective medium for learning a skill such as coding.â

âOhan Emannuel, UI designer & Lead Front End Dev at Kudi.ai

âI spend my days and nights on Educative. It is indispensable. It is such a unique and reader-friendly site, resources available for learners on Educative is well organized and deep. It helps break down tricky programming concepts into simple chunks and exercises for practice to solidify the learning experience.â

âSouvik Kundu, Front End Dev

Join the 1M+ developers and engineering teams already growing with Educative.

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## What Language Is The Course Presented In

In this dynamic programming course, solutions are not only implemented in Javascript. The same solution is represented in Python, Java and C++ as well, which makes the course suitable for any developer with some knowledge of these languages.

The course is filled with several illustrations to help you visualize the problem before attempting to code it out. Rather than just having you try to memorize solutions, youll be walked through five underlying DP patterns that can then be applied to solve 35+ DP problems.

In each pattern, the course presents a recursive or non-dynamic approach to solve the problem, which is the best way to start solving a DP problem. Once we have a recursive solution, well then apply the advanced DP methods of Memoization and Tabulation.

The practice problems in this course were carefully chosen, covering the most frequently asked DP questions in dynamic programming interviews.

## How To Start Your Interview Prep

I think that for most people starting out in this interview prep process, LeetCode is pretty hard. Here are two possible starting problems, though the best point of entry is admittedly Cracking the Coding Interview.

• FizzBuzz on LeetCode. I recommend it because it should not require any additional interview preparation, and will help you familiarize yourself with the LeetCode platform.

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System Design interviews are arguably some of the most difficult for software engineers.

Making it even more challenging, many college computer science courses and coding bootcamps dont include system design in the curriculum.

But Grokking the System Design Interview bridges that gap.

Its designed to expose you to the most important elements of system design asked in FAANG-level interviews.

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## One Dp Solution: Bottom

DP 1. Introduction to Dynamic Programming | Memoization | Tabulation | Space Optimization Techniques

Lets populate our dp array from the above solution, working in a bottom-up fashion. We want to find the maximum profit for every sub-array and for every possible capacity.

For every possible capacity c , there are two options:

• Exclude the item. We will take whatever profit we get from the sub-array excluding this item: dp
• Include the item if its weight is not more than the c. Well include its profit plus whatever profit we get from the remaining capacity: profit + dp]
• Take the maximum of the above two values:

dp = max

Heres the code:

`public class Knapsack }// maximum profit will be in the bottom-right corner.return dp }public static void main  int weights =  System.out.println) System.out.println) }}`

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## Grokking The Coding Interview: Patterns For Coding Questions

This course on by Design Gurus expands upon the questions on the recommended practice questions but approaches the practicing from a questions pattern perspective, which is an approach I also agree with for learning and have personally used to get better at coding interviews. The course allows you to practice selected questions in Java, Python, C++, JavaScript and also provides sample solutions in those languages along with step-by-step visualizations. Learn and understand patterns, not memorize answers!Get lifetime access now

## Module 3 Common Dynamic Programming Problems

• Use active studying techniques to cut your study time in half while making the concepts stick so you never worry about blanking when youre in the interview.
• Apply the FAST Method and see different dynamic programming patterns with 5 common practice problems, so youre never caught off guard in your interview.
• Experiment with the problem solutions yourself using the Github repo and runnable Java code for every problem in the course and never forget how to solve the problems interview.

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## Preparing For Coding Interview Here Are 20 Dynamic Programming Problems To Test Your Skills And Prepare Well

Hello guys, if you are preparing for coding interviews then there are two topics which I would say you must pay special attention, one is system Design and other is Dynamic Programming, both are difficult to master but extremely important for tech interviews.

In the past, I have shared best Dynamic Programming Courses as well as best System design courses, books, and System design interview questions and in this article, I am going to share best Dynamic Programming questions from interviews for practice. You can solve these questions to not just learn Dynamic Programming but also master it.

Dynamic Programming is one of the toughest concepts to master for programmers but at the same time, its quite important to crack any programming job interviews.

Nowadays, you will find at least one Dynamic programming coding problem on every coding interview and thats where most of the programmers get stuck.

They try to solve the problem using techniques like divided and conquer but ultimately fail because its difficult to come to a solution to such problems unless you have solved a decent number of dynamic programming-based coding questions.

This is very similar to system design questions which look easy but when you try to solve them you often find yourself stuck and thats why I suggest you practice as much as possible.