Complete frequency

Weekly Challenge 276

Each week Mohammad S. Anwar sends out The Weekly Challenge, a chance for all of us to come up with solutions to two weekly tasks. My solutions are written in Python first, and then converted to Perl. It's a great way for us all to practice some coding.

Challenge, My solutions

Task 1: Complete Day

Task

You are given an array of integers, @hours.

Write a script to return the number of pairs that forms a complete day. A complete day is defined as a time duration that is an exact multiple of 24 hours.

My solution

For this task, I could have used the combinations generator to create the pairs, but that seems like overkill for this task.

Instead I use a double loop. The other loop - with the variable i - is from 0 to two less than the number of items in the list. The inner loop - with the variable j - is from one more than i to one less than the number of items in the list. This method ensures that we use every possible pairs.

I have a variable called count which records the number of pairs when the combination of hours is a multiple of 24.

def complete_day(hours: list) -> int:
    count = 0
    items = len(hours)

    for i in range(items-1):
        for j in range(i+1, items):
            if (hours[i] + hours[j]) % 24 == 0:
                count += 1

    return count

Examples

$ ./ch-1.py 12 12 30 24 24
2

$ ./ch-1.py 72 48 24 5
3

$ ./ch-1.py 12 18 24
0

Task 2: Maximum Frequency

Task

You are given an array of positive integers, @ints.

Write a script to return the total number of elements in the given array which have the highest frequency.

My solution

For this task, I use the Counters function to turn the the list into a dict of frequencies. The key is the integer, the value is the number of times it occurs. Perl doesn't have a similar function, so I do this manually in my Perl solution.

The steps I take is as follows:

1. Calculate the frequency of each integer, and store this in the freq dict (hash in Perl).
2. Find the maximum frequency, and store this as max_freq.
3. Count the number of elements in the freq dict that have max_freq. This is stored as the elements variable.
4. Return the product of the max_freq and elements variable. This represents the number of items in the original array that have the highest frequency.

def maximum_frequency(ints: list) -> str:
    freq = Counter(ints)
    max_freq = max(freq.values())
    elements = sum(1 for v in freq.values() if v == max_freq)
    return elements * max_freq

Examples

$ ./ch-2.py 1 2 2 4 1 5
4

$ ./ch-2.py 1 2 3 4 5
5