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| 1 | +def stalin_sort(sequence: list[int]) -> list[int]: |
| 2 | +""" |
| 3 | +Stalin Sort algorithm: Removes elements that are out of order. |
| 4 | +Elements that are not greater than or equal to the previous element are discarded. |
| 5 | +Reference: https://medium.com/@kaweendra/the-ultimate-sorting-algorithm-6513d6968420 |
| 6 | +""" |
| 7 | + """ |
| 8 | + Sorts a list using the Stalin sort algorithm. |
| 9 | +
|
| 10 | + >>> stalin_sort([4, 3, 5, 2, 1, 7]) |
| 11 | + [4, 5, 7] |
| 12 | +
|
| 13 | + >>> stalin_sort([1, 2, 3, 4]) |
| 14 | + [1, 2, 3, 4] |
| 15 | +
|
| 16 | + >>> stalin_sort([4, 5, 5, 2, 3]) |
| 17 | + [4, 5, 5] |
| 18 | +
|
| 19 | + >>> stalin_sort([6, 11, 12, 4, 1, 5]) |
| 20 | + [6, 11, 12] |
| 21 | +
|
| 22 | + >>> stalin_sort([5, 0, 4, 3]) |
| 23 | + [5] |
| 24 | +
|
| 25 | + >>> stalin_sort([5, 4, 3, 2, 1]) |
| 26 | + [5] |
| 27 | +
|
| 28 | + >>> stalin_sort([1, 2, 3, 4, 5]) |
| 29 | + [1, 2, 3, 4, 5] |
| 30 | +
|
| 31 | + >>> stalin_sort([1, 2, 8, 7, 6]) |
| 32 | + [1, 2, 8] |
| 33 | + """ |
| 34 | + if any(x < 0 for x in sequence): |
| 35 | + raise ValueError("Sequence must only contain non-negative integers") |
| 36 | + |
| 37 | + result = [sequence[0]] |
| 38 | + for i in range(1, len(sequence)): |
| 39 | + if sequence[i] >= result[-1]: |
| 40 | + result.append(sequence[i]) |
| 41 | + |
| 42 | + return result |
| 43 | + |
| 44 | + |
| 45 | +if __name__ == "__main__": |
| 46 | + import doctest |
| 47 | + doctest.testmod() |
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