How to count even and odd frequencies in a number stream

Counting the frequency of numbers in a dataset or a number stream is a fundamental operation in data analysis and statistics. In real life, this frequency counting algorithm is applied to solve complex business problems.

For example, consider an inventory store where customers purchase their daily use products. We can utilize frequency counting to identify the best selling products, track customer visit frequencies, monitor product stockout frequencies, and analyze purchase patterns over time.

In this Answer, we’ll take a stream of numbers and count the frequencies of both even and odd numbers in it.

Even and odd frequencies

We’ll use two variables to count even and odd numbers within the stream of numbers. We’ll iterate through the entire stream, checking each number to determine whether it’s even or odd. If it’s even, we’ll increment the even count variable by 1, and if it’s odd, we’ll increment the odd count variable by 1.

Code example 1

Here’s a code example:

# Initialize count variables
evenCount = 0
oddCount = 0
# Define a stream of numbers
numberStream = [2, 5, 8, 7, 10, 13, 6, 3]
# Iterate the number stream
for number in numberStream:
    # If the number is even, increment evenCount by 1
    if number % 2 == 0:
        evenCount += 1
    else:
      # If the number is odd, increment oddCount by 1
        oddCount += 1
# Display the frequncy
print("Even frequency:", evenCount)
print("Odd frequency:", oddCount)

Code explanation

  • Lines 2–3: We initialized the evenCount and oddCount variables with 0.

  • Line 5: We list the numberStream array initialized with the numbers.

  • Lines 9–15: We use the for loop to iterate through the list of numbers, checking each number. If the number is even, it increments the evenCount variable by 1 and if the number is odd, it increments the oddCount variable by 1.

  • Lines 18–19: We print the frequency of both even and odd numbers.

Code example 2

In this code example, we solve a problem using a function and AND method. We modify the code to check if each number in a list is even or odd. 

def CountingEvenOdd(numberStream, size): 
    evenCount = 0
    oddCount = 0
  
    for i in range(size): # Iterate the number stream
        if (numberStream[i] & 1 == 1):  # If the number is odd, incerement oddCount by 1
            oddCount += 1
        else: 
            evenCount += 1. # If the number is even, incerement evenCount by 1
  
    print("Number of even elements = ", 
          evenCount) 
    print("Number of odd elements = ", 
          oddCount) 
  
  
numberStream = [2, 3, 4, 5, 6]  # Define a stream of numbers
n = len(numberStream) 
  
CountingEvenOdd(numberStream, n) # Call the function

Code explanation

  • Line 1: We define a function named CountingEvenOdd() with two parameters: numberStream (a list of numbers) and size (the size of the list).

  • Line 5: We start a loop to iterate through each value in the numberStream list.

  • Line 6: We implement the condition: if the least significant bit of the number at index i is 1, and the bitwise AND operation with 1 results in 1, then the number at the index i is odd; otherwise even.

  • Line 18: We compute the length of the numberStream list and assign it to the variable n.

  • Line 21: We call the CountingEvenOdd() function with the numberStream list and its length n as arguments.

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