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Setting a Matrix to Zero in Javaby@ishitajuneja
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Setting a Matrix to Zero in Java

by Ishita JunejaFebruary 10th, 2023
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The set Matrix zeroes problem is one of the top coding questions asked in almost every coding interview. From Brute Force to HashMaps, the set Matrix zero problems in programming can be solved using only two programming approaches. Let's find out the approaches that will help you effectively set the values to zero within a matrix.
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Did you know?

Matrices in Java are also referred to as 2D arrays. Well, this is because the same components displayed on an array are organized in rows and columns in a matrix that forms a rectangular structure.


Usually, the matrices are used for storing all the complex digits within a program that are further used for carrying out arithmetic applications such as addition, subtraction, multiplication, and more.


Sometimes, the programmers are also required to set all the values of a particular matrix to 0. This in other terms is known as the set matrix zeroes problem.


This is one of the most highly discussed problems in coding and technical interviews.

Hence, if you are preparing for a coding interview and would like to learn a few simple approaches for setting a matrix value to 0, then keep reading.



What Does It Mean to Set Matrix Zeroes in Java?

Have you ever noticed how the numbers in a Sudoku are arranged in rows and columns of equal numbers of characters, making it a perfect square?


Well, the structure of a matrix in the context of computer programming resembles similar characteristics to a sudoku square with the only difference being that the shape of a matrix is rectangular.


Matrices are used for arranging the entries or the elements of data that usually represent a mathematical object.


So basically, a matrix can essentially be defined as a set of numbers that are arranged in columns and rows in order to form a rectangular shape.


So, what would a zero-column matrix represent?

Well, the Matrices containing a zero column would signify that all of its elements or entries are equal to zero. In other terms, such matrices are also referred to as zero matrices in computer programming.


Did you know?


Like all the other data structures, you can also manipulate the matrices (such as setting them to zero value) using different logic. The Set Matrix zeroes problem is the discussion we shall be having next in the following column. Let's find out the approaches that will help you effectively set the values to zero within a matrix.


Which Algorithms Can Be Used to Set Matrices to Zero?

The set Matrix zero problems are one of the top coding questions asked in almost every coding interview. From Brute Force to HashMaps, the set Matrix zero problems in programming can be solved using only two programming approaches


If you are not acquainted with these methods, check out a quick overview of their definitions.



  1. **Brute Force Approach

Brute Force is a simple function that focuses on approaching the problem by dividing the input into several subarrays and seeking every single input individually. In the context of setting the matrix to zero, we will be using the auxiliary space and the nested loops to their optimal efficiency. The nested loops are ideal for dividing the problem into subproblems by inserting the elements of the input into loops that can be traversed later.



  1. **Using Hash Table

A HashMap is essentially a structure of rows and columns that are used for storing the entries so that the efficiency of finding the solution becomes relatively easier. The contents of the array or the entries are iterated on a HashMap. Hence, in this approach, we will be using the Hash Table in order to store the status of the rows and columns.


  1. Using In-Place Hashing


In-place hashing is a more in-depth method where the hash is used to store the values of the elements or entries within the first line of the rows and columns of the matrix. We will be employing two different variables for storing the elements in the first row and column namely: firstRow and firstColumn. For a more in-depth analysis of the working mechanism of the algorithms for these approaches, check out the next section of this blog.



How to Apply the Algorithms That Set Matrices to Zero in Java

As discussed in the previous section, the set Matrix zero problems can be tackled by simply using the Brute Force Approach and by implementing a Hash Table.


Let's discuss the in-depth analysis of the algorithms for these approaches and you can decide for yourself how their time complexities compare to one another.


Method 1: Using Brute Force Approach


Here's how the algorithm for Brute Force shall be implemented:


  • Start with creating a temporary matrix and name it as m*n.
  • Initialize the elements of this matrix with 1.
  • Now, travel to the first matrix that you were initially provided as an input and set the positions of its elements into row 1 and column j along with 0 in the newly created matrix.
  • Finally, you can proceed and continue to copy all the elements as such in the temporary matrix from the initial matrix and print the program once the process is completed.\


Method 2: Using Hash Table


The algorithm for the Hash Table would look something as follows:


  • Start with creating two different Hash Tables.
  • Next up, you will have to initialize the value of the rows and columns of the table to false.
  • Further, you may iterate on the initial matrix and set all the values to 0.
  • Complete the entire process until all the values return 0 input.\


Method 3: Using In-Place Hashing


Here's how you can implement the in-place hashing algorithm:


  • Start by defining the two variables i.e firstRow and firstColumn.
  • Set both variables to false.
  • Using the Hash Table to store all the false values from the rows and columns
  • Finally, update the value of the first row and column on the Hash Map.