JavaScript program to calculate the frequency of even and odd numbers in a matrix

In this tutorial, we will implement a JavaScript program to find the frequency of even and odd numbers. We will be given a 2D matrix of size MXN and we have to find the frequency of all odd and even numbers present in the matrix (meaning the number of elements present). We will see two methods, one is the brute force method (using a for loop) and the other is the bitwise AND operator method.

Problem Introduction

In this problem we are given a 2D matrix which contains odd and even numbers in an unsorted manner and we have to find the frequency of odd and even numbers in the 2D matrix. For example -

In this problem we are given a 2D matrix which contains odd and even numbers in an unsorted manner and we have to find the frequency of odd and even numbers in the 2D matrix. For example -

Row ( m ) = 3; Column ( n ) = 3;
Matrix = [[1, 2, 3], 
          [4, 5, 6], 
          [7, 8, 9]];

According to the given matrix of size 3X3, we get the frequency of odd and even numbers as -

Frequency of odd number =  5 
Frequency of even number = 4

We can return the frequencies, we can simply print them as is, let's move on to the solution to the problem -

Method 1 (using mod ‘%’ operator)

In this approach, we simply iterate over the matrix using nested for loops. While looping through the for loop, we calculated the frequency of odd and even numbers in the 2D matrix. To check if the value is odd or even we use the mod ('%') operator which basically takes the number modulo 2, if the mod value is '1' it means it is odd otherwise it is even and finally , we return the odd and even counts. Let us go to the code of this method to understand better.

Example

Here is a JavaScript program to find the frequency of even and odd numbers in a matrix using pattern operators -

let MAX = 100;
// function for calculating frequency
function freq(arr,row,col) {
   let evenNum = 0, oddNum = 0;
   for (let i = 0; i < row; ++i) {
      for (let j = 0; j < col; ++j) {
         // checking evenNum or oddNum using mod operator
         if ((arr[i][j] % 2) == 0)
         ++evenNum;
         else
         ++oddNum;
      }
   }
   // print Frequency of odd and even numbers
   console.log(" Frequency of odd numbers = " + oddNum );
   console.log(" Frequency of even numbers = " + evenNum );
}
let m = 3, n = 3;
let arr = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
freq(arr, m, n);

Time and space complexity

The time complexity of the above code is O(M*N), where M is the row size of the two-dimensional matrix and N is the column size.

The space complexity of the above code is O(1) because we used int values ​​to store only integers.

Method 2 (using bitwise ‘&’ operator)

In this approach, we will simply iterate over the matrix using nested for loops. While looping through the for loop, we calculated the frequency of odd and even numbers in the 2D matrix. To check if the value is odd or even, we use the bitwise ("&") operator, which basically takes the bitwise value of the number as 1, if the bitwise value is "0", it means it is even, otherwise it means it is odd number. Finally we return the count of odd and even numbers. Let us go to the code of this method to understand better.

Example

Here is a JavaScript program that uses the bitwise & operator to find the frequency of even and odd numbers in a matrix -

let MAX = 100;
// function for calculating frequency
function freq(arr,row,col) {
   let evenNum = 0, oddNum = 0;
   for (let i = 0; i < row; ++i) {
      for (let j = 0; j < col; ++j) {
         // checking evenNum or oddNum using bitwise operator
         if ((arr[i][j] & 1) == 0)
         ++evenNum;
         else
         ++oddNum;
      }
   }
   // print Frequency of odd and even numbers
   console.log(" Frequency of odd numbers = " + oddNum );
   console.log(" Frequency of even numbers = " + evenNum );
}
let m = 3, n = 3;
let arr = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
freq(arr, m, n);

Time and space complexity

The time complexity of the above code is O(M*N), where M is the row size of the two-dimensional matrix and N is the column size.

The space complexity of the above code is O(1) because we used int values ​​to store only integers.

in conclusion

In this tutorial, we implemented a JavaScript program to find the frequency of even and odd numbers in a two-dimensional matrix. We are given a 2D matrix of size NXM and we have to find the frequencies of odd and even values ​​of this 2D matrix. We have seen two methods, one is using the mod operator and the other is using the bitwise operators.

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