Data-Structures-And-Algorithms/10-DutchNationalFlagProblem.py at master · fastalana/Data-Structures-And-Algorithms · GitHub

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def sort_012(input_list):
    """
    Given an input array consisting on only 0, 1, and 2, sort the array in a single traversal.

    Args:
       input_list(list): List to be sorted
    """
    index = 0
    next_0 = 0
    next_2 = len(input_list) - 1

    while index <= next_2:
        if input_list[index] == 0:
            input_list[index] = input_list[next_0] # Makes sure we don't accidentially overwrite a value
            input_list[next_0] = 0
            next_0 += 1
            index += 1
        elif input_list[index] == 2:
            input_list[index] = input_list[next_2] # Makes sure we don't accidentially overwrite a value
            input_list[next_2] = 2
            next_2 -= 1
        else:
            index += 1

    return input_list

def test_function(test_case):
    sorted_array = sort_012(test_case)
    if sorted_array == sorted(test_case):
        print("Pass")
    else:
        print("Fail")

test_function([])

test_function([0])
test_function([1])
test_function([2])

test_function([0, 0])
test_function([0, 1])
test_function([2, 1])

test_function([0, 1, 2])
test_function([1, 2, 0])
test_function([2, 1, 0])

test_function([0, 0, 2, 2, 2, 1, 1, 1, 2, 0, 2])
test_function([2, 1, 2, 0, 0, 2, 1, 0, 1, 0, 0, 2, 2, 2, 1, 2, 0, 0, 0, 2, 1, 0, 2, 0, 0, 1])
test_function([0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2])