Python Program for Frequencies of even and odd numbers in a matrix

Given a matrix of order m*n then the task is to find the frequency of even and odd numbers in matrix 
Examples: 

Input : m = 3, n = 3
        { 1, 2, 3 }, 
        { 4, 5, 6 }, 
        { 7, 8, 9 }
Output : Frequency of odd number =  5 
         Frequency of even number = 4


Input :   m = 3, n = 3
         { 10, 11, 12 },
         { 13, 14, 15 },
         { 16, 17, 18 }
Output : Frequency of odd number  =  4 
         Frequency of even number  = 5

Python3

# Python Program to Find the frequency
# of even and odd numbers in a matrix

MAX=100

# Function for calculating frequency
def freq(ar, m, n):
    even = 0
    odd = 0

    for i in range(m):
        for j in range(n):

            # modulo by 2 to check
            # even and odd
            if ((ar[i][j] % 2) == 0):
                even += 1
            else:
                odd += 1

    # print Frequency of numbers
    print(" Frequency of odd number =", odd)
    print(" Frequency of even number =", even)


# Driver code
m = 3
n = 3

array = [ [ 1, 2, 3 ],
        [ 4, 5, 6 ],
        [ 7, 8, 9 ] ]

freq(array, m, n)

# This code is contributed
# by Anant Agarwal.

Output: 

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

Time Complexity: O(m*n)
Auxiliary Space: O(1)

Please refer complete article on Frequencies of even and odd numbers in a matrix for more details!

Method: Using bitwise & operator

Python3

# Python Program to Find the frequency
# of even and odd numbers in a matrix using bitwise & operator.

MAX=100

# Function for calculating frequency
def freq(ar, m, n):
    even = 0
    odd = 0

    for i in range(m):
        for j in range(n):

            # bitwise & 1 to check
            # even and odd
            if ((ar[i][j] & 1) == 0):
                even += 1
            else:
                odd += 1

    # print Frequency of numbers
    print(" Frequency of odd number =", odd)
    print(" Frequency of even number =", even)


# Driver code
m = 3
n = 3

array = [ [ 1, 2, 3 ],
        [ 4, 5, 6 ],
        [ 7, 8, 9 ] ]

freq(array, m, n)

# This code is contributed
# by vinay pinjala.

Output

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

Time Complexity: O(m*n)
Auxiliary Space: O(1)

Approach#3: Using sum

We start by defining the input matrix. We use list comprehension to flatten the matrix into a 1D list. We then use the sum() function along with a generator expression to count the number of odd and even numbers in the flattened list. Finally, we print the frequency of odd and even numbers.

1. Start with a matrix of size m x n.
2. Flatten the matrix into a 1D list using list comprehension.
3. Initialize two variables, odd_freq, and even_freq, to 0.
4. Iterate through the flattened list and increment odd_freq by 1 if the element is odd, and increment even_freq by 1 if the element is even.
5. Print the frequency of odd and even numbers.

Python3

# Example input matrix
matrix = [[10, 11, 12],
          [13, 14, 15],
          [16, 17, 18]]

# Using list comprehension to flatten
# the matrix into a 1D list
flat_list = [num for row in matrix for num in row]

# Finding the frequencies
odd_freq = sum(1 for num in flat_list if num % 2 != 0)
even_freq = sum(1 for num in flat_list if num % 2 == 0)

# Printing the output
print("Frequency of odd numbers:", odd_freq)
print("Frequency of even numbers:", even_freq)

Output

Frequency of odd numbers: 4
Frequency of even numbers: 5

Time Complexity; O(n²), where n is the length of one side of the matrix. This is because the program iterates over each element in the matrix once.

Space Complexity: O(n²), since it creates a 1D list with n^2 elements to store the flattened matrix. However, the space required for the odd_freq and even_freq variables is constant, since they only store two integers.