【06】Sort Array by Element Frequency.py

# =====================================================
# --*-- coding: utf-8 --*--
# @Author  : TRHX
# @Blog    : www.itrhx.com
# @CSDN    : itrhx.blog.csdn.net
# @FileName: 【06】Sort Array by Element Frequency.py
# =====================================================


from collections import Counter


def frequency_sort(items):
    items2 = []
    items = Counter(items).most_common()
    for i in items:
        items2.extend([i[0]] * i[1])
    return items2


if __name__ == '__main__':
    print("Example:")
    print(frequency_sort([4, 6, 2, 2, 6, 4, 4, 4]))

    # These "asserts" are used for self-checking and not for an auto-testing
    assert list(frequency_sort([4, 6, 2, 2, 6, 4, 4, 4])) == [4, 4, 4, 4, 6, 6, 2, 2]
    assert list(frequency_sort(['bob', 'bob', 'carl', 'alex', 'bob'])) == ['bob', 'bob', 'bob', 'carl', 'alex']
    assert list(frequency_sort([17, 99, 42])) == [17, 99, 42]
    assert list(frequency_sort([])) == []
    assert list(frequency_sort([1])) == [1]
    print("Coding complete? Click 'Check' to earn cool rewards!")