5 Best Ways to Check if Frequency of Each Digit Is Less Than the Digit in Python

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πŸ’‘ Problem Formulation: You may encounter a scenario in coding where you need to verify if the frequency of each digit in a number is less than the value of the digit itself. For instance, given the number 1223334444, the output should be False because the frequency of ‘4’ is equal to 4, not less than it. We aim to present several Python methods to solve this issue.

Method 1: Using Count in a Loop

This method involves iterating over each unique digit in the given number, counting its occurrences, and checking if these occurrences are less than the digit. A function, is_frequency_less_than_digit, takes a string representation of the number and provides a boolean answer.

Here’s an example:

def is_frequency_less_than_digit(number):
    for digit in set(number):
        if number.count(digit) >= int(digit):
            return False
    return True

print(is_frequency_less_than_digit('1223334444'))

Output:

False

In the code snippet, we define a function that checks each unique digit’s frequency against its value. It returns False as soon as it finds a digit with a frequency not less than the digit, confirming the condition is not met for the entire number.

Method 2: Using Collections Counter

This method uses Python’s collections.Counter to count the frequency of digits and compare them to their values. The Counter creates a dictionary with digits as keys and their frequencies as values. We then iterate through the dictionary to perform our check.

Here’s an example:

from collections import Counter

def is_frequency_less_than_digit(number):
    digit_count = Counter(number)
    return all(int(digit) > count for digit, count in digit_count.items())

print(is_frequency_less_than_digit('1223334444'))

Output:

False

The code defines a function utilizing the Counter class to simplify the frequency counting process. The all function helps succinctly determine if all digit frequencies meet the condition, leading to a clean and efficient solution.

Method 3: Using a Dictionary Comprehension

Building off the Counter method, this approach uses dictionary comprehension to create a frequency dictionary. The suitability is then verified by comparing each digit and its frequency within a generator expression passed to the all function.

Here’s an example:

def is_frequency_less_than_digit(number):
    digit_freq = {digit: number.count(digit) for digit in number}
    return all(int(digit) > freq for digit, freq in digit_freq.items())

print(is_frequency_less_than_digit('1223334444'))

Output:

False

The snippet showcases how dictionary comprehension can create a frequency dictionary, then checks the condition with a generator within the all function. This method blends manual iteration with Python’s elegant comprehension and functional features.

Method 4: Using Map with Lambda

This approach iterates digits using map with a lambda function, comparing each digit to its frequency. It’s a functional programming method that applies the same comparison logic over the entire number string.

Here’s an example:

def is_frequency_less_than_digit(number):
    return all(map(lambda digit: int(digit) > number.count(digit), number))

print(is_frequency_less_than_digit('1223334444'))

Output:

False

Through map, we apply a lambda function across the number string, checking the required condition for each digit, and the all function again ensures all digits meet this condition. Despite being functional and concise, this method may perform count operation multiple times for same digits, which can be inefficient for large numbers with repeated digits.

Bonus One-Liner Method 5: List Comprehension and Set

Combining powers of a list comprehension, set, and the all function to provide a one-liner solution, this method performs a direct frequency check for each unique digit against its integer value.

Here’s an example:

print(all(int(digit) > '1223334444'.count(digit) for digit in set('1223334444')))

Output:

False

This nifty one-liner uses a list comprehension within the all function to check the condition, exploiting the concise nature of Python’s syntax to deliver a neat, albeit packed, solution in a single line of code.

Summary/Discussion

The best approach depends on the specifics of your situation:

  • Method 1: Loop and Count. Simple and straightforward. Can be inefficient for large numbers with repeated digits due to multiple counts.
  • Method 2: Collections Counter. Utilizes Python’s standard library for more concise code. Offers good readability and efficiency.
  • Method 3: Dictionary Comprehension. A blend of manual counting with Python’s advanced features. Well-suited for Pythonistas comfortable with comprehension and functional programming.
  • Method 4: Map with Lambda. Leverages functional programming for a more abstract approach. May suffer from redundancies in digit frequency checks.
  • Bonus Method 5: One-Liner. Extremely concise, but potentially less readable for beginners. Efficient when maintaining readability and one-liner elegance is not crucial.