problem_360.py

from heapq import heappush, heappop


def interleave_playlist(ranked_listings):
    scores = dict()
    for listing in ranked_listings:
        num_songs = len(listing)
        total_points = ((num_songs + 1) * num_songs) // 2
        for rank, song in enumerate(listing):
            if song not in scores:
                scores[song] = 0
            scores[song] += total_points / (rank + 1)

    sorted_scored_tuples = list()
    for song, score in scores.items():
        heappush(sorted_scored_tuples, (score, song))

    interleaved = list()
    while sorted_scored_tuples:
        _, song = heappop(sorted_scored_tuples)
        interleaved.append(song)

    return interleaved[::-1]


# Tests
ranked_listings = [
    [1, 7, 3],
    [2, 1, 6, 7, 9],
    [3, 9, 5]
]
assert interleave_playlist(ranked_listings) == [2, 1, 3, 7, 9, 6, 5]