Tabulation vs Memoization

There are two different ways to store the values so that the values of a sub-problem can be reused. Here, will discuss two patterns of solving dynamic programming (DP) problems: 

  • Tabulation: Bottom Up
  • Memoization: Top Down

Before getting to the definitions of the above two terms consider the following statements:

  • Version 1: I will study the theory of DP from w3wiki, then I will practice some problems on classic DP and hence I will master DP.
  • Version 2: To Master DP, I would have to practice Dynamic problems and practice problems – Firstly, I would have to study some theories of DP from w3wiki

Both versions say the same thing, the difference simply lies in the way of conveying the message and that’s exactly what Bottom-Up and Top-Down DP do. Version 1 can be related to Bottom-Up DP and Version-2 can be related to Top-Down DP.

     Tabulation       Memoization   
State State transition relation is difficult to think State Transition relation is easy to think
Code Code gets complicated when a lot of 
conditions are required
Code is easy and less complicated
 
Speed Fast, as we directly access previous states from the table Slow due to a lot of recursive calls and return statements
Subproblem solving If all subproblems must be solved at least once, a bottom-up dynamic programming algorithm usually outperforms a top-down memoized algorithm by a constant factor If some subproblems in the subproblem space need not be solved at all, the memoized solution has the advantage of solving only those subproblems that are definitely required 
Table entries In the Tabulated version, starting from the first entry, all entries are filled one by one Unlike the Tabulated version, all entries of the lookup table are not necessarily filled in Memoized version. The table is filled on demand.
Approach Generally, tabulation(dynamic programming) is an iterative approach On the other hand, memoization is a recursive approach.

Dynamic Programming (DP) Tutorial with Problems

Dynamic Programming (DP) is defined as a technique that solves some particular type of problems in Polynomial Time. Dynamic Programming solutions are faster than the exponential brute method and can be easily proved their correctness.

Important Topics in Dynamic Programming Tutorial

  • Characteristics of Dynamic Programming Algorithm:
  • What is the difference between a Dynamic programming algorithm and recursion?
  • Techniques to solve Dynamic Programming Problems:
  • Tabulation(Dynamic Programming) vs Memoization:
  • How to solve a Dynamic Programming Problem?
  • How to solve Dynamic Programming problems through Example?
  • Greedy approach vs Dynamic programming
  • Some commonly asked problems in Dynamic programming:
  • FAQs about Dynamic Programming Algorithm:

Dynamic Programming is mainly an optimization over plain recursion. Wherever we see a recursive solution that has repeated calls for the same inputs, we can optimize it using Dynamic Programming. The idea is to simply store the results of subproblems so that we do not have to re-compute them when needed later. This simple optimization reduces time complexities from exponential to polynomial.

Introduction to Dynamic Programming – Data Structures and Algorithm Tutorials

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Characteristics of Dynamic Programming Algorithm:

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What is the difference between a Dynamic programming algorithm and recursion?

In general, dynamic programming (DP) is one of the most powerful techniques for solving a certain class of problems.  There is an elegant way to formulate the approach and a very simple thinking process, and the coding part is very easy.  Essentially, it is a simple idea, after solving a problem with a given input, save the result as a reference for future use, so you won’t have to re-solve it.. briefly ‘Remember your Past’ :).  It is a big hint for DP if the given problem can be broken up into smaller sub-problems, and these smaller subproblems can be divided into still smaller ones, and in this process, you see some overlapping subproblems.  Additionally, the optimal solutions to the subproblems contribute to the optimal solution of the given problem (referred to as the Optimal Substructure Property).  The solutions to the subproblems are stored in a table or array (memoization) or in a bottom-up manner (tabulation) to avoid redundant computation. The solution to the problem can be constructed from the solutions to the subproblems. Dynamic programming can be implemented using a recursive algorithm, where the solutions to subproblems are found recursively, or using an iterative algorithm, where the solutions are found by working through the subproblems in a specific order....

Techniques to solve Dynamic Programming Problems:

In dynamic programming, problems are solved by breaking them down into smaller ones to solve the larger ones, while recursion is when a function is called and executed by itself. While dynamic programming can function without making use of recursion techniques, since the purpose of dynamic programming is to optimize and accelerate the process, programmers usually make use of recursion techniques to accelerate and turn the process efficiently. When a function can execute a specific task by calling itself, receive the name of the recursive function. In order to perform and accomplish the work, this function calls itself when it has to be executed. Using dynamic programming, you can break a problem into smaller parts, called subproblems, to solve it. Dynamic programming involves solving the problem for the first time, then using memoization to store the solutions. Therefore, the main difference between the two techniques is their intended use; recursion is used to automate a function, whereas dynamic programming is an optimization technique used to solve problems. Recursive functions recognize when they are needed, execute themselves, then stop working. When the function identifies the moment it is needed, it calls itself and is executed; this is called a recursive case. As a result, the function must stop once the task is completed, known as the base case. By establishing states, dynamic programming recognizes the problem and divides it into sub-problems in order to solve the whole scene. After solving these sub-problems, or variables, the programmer must establish a mathematical relationship between them. Last but not least, these solutions and results are stored as algorithms, so they can be accessed in the future without having to solve the whole problem again....

Tabulation vs Memoization:

1. Top-Down(Memoization):...

How to solve a Dynamic Programming Problem?

There are two different ways to store the values so that the values of a sub-problem can be reused. Here, will discuss two patterns of solving dynamic programming (DP) problems:...

How to solve Dynamic Programming problems through Example?

To dynamically solve a problem, we need to check two necessary conditions:...

Greedy approach vs Dynamic programming

...

Some commonly asked problems in Dynamic programming:

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FAQs about Dynamic Programming Algorithm:

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Conclusion:

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