solution.py

# Hi! Welcome to my first kata.

# In this kata the task is to take a list of integers (positive and negative) and split them according to a simple rule;
# those ints greater than or equal to the key, and those ints less than the key
# (the itself key will always be positive).

# However, in this kata the goal is to sort the numbers IN PLACE,
# so DON'T go messing around with the order in with the numbers appear.

# You are to return a nested list. If the list is empty, simply return an empty list.

# Confused? Okay, let me walk you through an example...

# The input is: [1, 1, 1, 0, 0, 6, 10, 5, 10], the key is: 6
# Okay so the first five numbers are less than the key, 6, so we group them together.
# [1, 1, 1, 0, 0]

# The next two numbers, 6 & 10, are both >= 6 to they belong in a seperate group,
# which we will add to the first group. Like so:
# [[1, 1, 1, 0, 0], [6, 10]]

# The next two numbers are 5 & 10. Since the key is 6 these two numbers form seperate groups,
# which we will add to the previous result. like so:
# [[1, 1, 1, 0, 0], [6, 10], [5], [10]]

# And voila! We're done.

# Here are a few more basic examples:
# group_ints([1, 0], key= 0)
# --> [[1,0]]

# group_ints([1, 0, -1, 5], key= 0)
# --> [[1, 0], [-1], [5]]

# group_ints([1, 0, -1, 5], key= 5)
# --> [[1, 0, -1], [5]]


def group_ints(numbers, key=0):
    r, group_less, group_more = [], [], []
    for _, v in enumerate(numbers):
        if v < key:
            if group_more:
                r.append(group_more)
                group_more = []
            group_less.append(v)

        else:
            if group_less:
                r.append(group_less)
                group_less = []
            group_more.append(v)

    if group_less:
        r.append(group_less)
    if group_more:
        r.append(group_more)

    # one line solution:
    # from itertools import groupby
    # return [list(group) for _, group in groupby(numbers, lambda v: v >= key)]

    return r