Question

In Python,

Q.

Write a function max_increase(seq) which takes as argument a sequence of numbers and returns the maximum increase from one element in the sequence to an element at a higher index.

Assumptions and restrictions:

• The function must return a number.
• If there is no increasing pair in the sequence, the function should return 0. This may happen for example if the sequence is decreasing, or if it contains fewer than 2 elements.
• You can assume that the argument is a sequence, and that its elements are numbers (integer or decimal), but other than that you should not make any assumptions. In particular, you should not assume that it is any particular type of sequence (list, array, etc) and use only operations that are applicable to all sequence types.

Test has to pass this function.

def test_max_increase():
    '''
    This function runs a number of tests of the max_increase function.
    If it works ok, you will just see the output ("all tests passed") at
    the end when you call this function; if some test fails, there will
    be an error message.
    '''

    assert max_increase([]) == 0.0, "empty list has no pair";
    assert max_increase([1]) == 0.0, "size-1 list has no pair";
    assert max_increase((1,2,3,2)) == 2.0;
    assert max_increase([1.0,3.0,1.0,2.0]) == 2.0;
    assert max_increase([3,-1,2,1]) == 3.0;
    assert max_increase([3,2,1,1]) == 0.0, "no increasing pair";
    assert max_increase([226, 264, 337, 364, 485, 529, 482]) == 303.0;

    btc_data = [ 6729.44, 6690.88, 6526.36, 6359.98, 6475.89, 6258.74,
                 6485.10, 6396.64, 6579.00, 6313.51, 6270.20, 6195.01,
                 6253.67, 6313.90, 6233.10, 6139.99, 6546.45, 6282.50,
                 6718.22, 6941.20, 7030.01, 7017.61, 7414.08, 7533.92,
                 7603.99, 7725.43, 8170.01, 8216.74, 8235.70, 8188.00,
                 7939.00, 8174.06 ]
    btc_data.reverse()
    assert abs(max_increase(tuple(btc_data))-589.45) < 1e-6;

    print("all tests passed")

Answer 1

def max_increase(seq):
    if len(seq) <= 1:
        return 0
    max_diff = None
    for i in range(len(seq)):
        diff = None
        for j in range(i + 1, len(seq)):
            if diff is None or seq[j] - seq[i] > diff:
                diff = seq[j] - seq[i]
        if max_diff is None or (diff is not None and diff > max_diff):
            max_diff = diff
    return max_diff


def test_max_increase():
    '''
    This function runs a number of tests of the max_increase function.
    If it works ok, you will just see the output ("all tests passed") at
    the end when you call this function; if some test fails, there will
    be an error message.
    '''

    assert max_increase([]) == 0.0, "empty list has no pair";
    assert max_increase([1]) == 0.0, "size-1 list has no pair";
    assert max_increase((1, 2, 3, 2)) == 2.0;
    assert max_increase([1.0, 3.0, 1.0, 2.0]) == 2.0;
    assert max_increase([3, -1, 2, 1]) == 3.0;
    assert max_increase([3, 2, 1, 1]) == 0.0, "no increasing pair";
    assert max_increase([226, 264, 337, 364, 485, 529, 482]) == 303.0;

    btc_data = [6729.44, 6690.88, 6526.36, 6359.98, 6475.89, 6258.74,
                6485.10, 6396.64, 6579.00, 6313.51, 6270.20, 6195.01,
                6253.67, 6313.90, 6233.10, 6139.99, 6546.45, 6282.50,
                6718.22, 6941.20, 7030.01, 7017.61, 7414.08, 7533.92,
                7603.99, 7725.43, 8170.01, 8216.74, 8235.70, 8188.00,
                7939.00, 8174.06]
    btc_data.reverse()
    assert abs(max_increase(tuple(btc_data)) - 589.45) < 1e-6;

    print("all tests passed")


test_max_increase()