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
    """
    zeros = []
    ones = []
    twos = []
    for input in input_list:
        if input == 0:
            zeros.append(input)
        elif input == 1:
            ones.append(input)
        elif input == 2:
            twos.append(input)
    # zeros.append(ones)
    # zeros.append(twos)
    zeros.extend(ones)
    zeros.extend(twos)
    return zeros
    pass