Java Program to Find the Frequency of Odd & Even Numbers in the Matrix - GeeksforGeeks

29 Oct, 2020
Matrix is simply a two-dimensional array. Just like in one-dimensional traversal operation is required to figure out. The task is to find the frequencies of odd and even number in the given matrix. 
The size of matrix is defined as product of numbers of columns and rows. So, the size of the matrix is m × n 
Here in the matrix
M = number of rows in the matrix
N = number of columns
Example:
Input : M = 3
    N = 5
Output: Odd Number Frequency  = 9
    Even Number Frequency = 6
    
Input : M = 3
    N = 3
    {{1, 2, 5},
     {6, 7, 9},
     {3, 2, 1}}
Output: Odd Number Frequency  = 6
    Even Number Frequency = 3    

Approach 
Initialize two counters as even = 0 & odd = 0
Traverse through every element present in the matrix and check whether (element % 2 == 0)
If Yes then increment even++
Else increment odd++
Below is the implementation of the approach in Java
Java
// Importing Classes/Filesimport java.io.*;  class GFG {      // Function to compute frequency of odd/even numbers    public static void findFreq(int[][] arr, int m, int n)    {        // Initializing the counter variables        int even = 0, odd = 0;          // Nested if loops        // Traversing through each        // element in the matrix        for (int i = 0; i < m; i++) {                        for (int j = 0; j < n; j++) {                  // Checking if the element                // is divisible by 2                if (arr[i][j] % 2 == 0) {                      // Increment even counter                    even++;                }                else {                      // Increment odd counter                    odd++;                }            }        }          // Printing Counts of Enen         // and odd numbers in matrix        System.out.println("Odd Number Frequency: " + odd);        System.out.println("Even Number Frequence: "                           + even);    }      // Main Driver Method    public static void main(String[] args)    {        // Providing inputs to the matrix        int m = 3, n = 5;        // Here, m = Number of rows,        // n = Number  of columns          // Entering elements in the matrix        int[][] arr = { { 3, 4, 5, 6, 3 },                        { 4, 3, 2, 7, 9 },                        { 1, 5, 7, 2, 4 } };          // Calling function to count frequency by        // passing inputs to the function findFreq        findFreq(arr, m, n);    }}
Odd Number Frequency: 9
Even Number Frequence: 6
Time Complexity: As the single-dimensional array is traversed it depends on the size of the array over which the operation performs because rest execution either is of the same order or taking some constant space in the memory(variables). Here the traversal is over all the elements of the row and for every row in the matrix. So it depends on the product of rows and columns. Hence, the time complexity is of order(degree)
Space Complexity: Just assigning memory to variables that later gets released with the scope of the variables. As no other auxiliary space is created for the operations to execute. Hence, the space required is constant which is released afterward. 1 is assigned by default hence space complexity is of order 1.  
Time Complexity  = O(Rows*Columns) or O(m * n)
Space Complexity = O(1)

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