3

我试图返回一个布尔值，它只在原始布尔值中给出最长的“真”出现，并将较短的“真”块替换为“假”。示例 a=[True, True, False, True , True, True, False]，我想返回 [False, False, False, True, True, True, False]。

我尝试了 more_itertools，它似乎有一些有趣的功能，但不确定如何为我的目的准确实现。

a=[True, True, False, True , True, True, False]

pred = lambda x: x in {True}

p=list(mit.run_length.encode(a))

>>>
Results in: (True,2),(False,1),(True,3),(False,1)

所以我最终想要自动得到的是（False，3），（True，3），（False，1）。有什么建议么？谢谢您的帮助

4

2 回答 2

3

Below solution should work after using more_itertools.run_length.

Essentially, the logic is to find the length of longest subsequence of True, and the location of that index in result list
then count the total elements before and after that longest subsequence, then construct the resultant list of tuples accordingly.

import more_itertools as mit

a=[True, True, False, True , True, True, False]

result = list(mit.run_length.encode(a))

#Find the length of longest subsequence of True, and the location if that index in result
max_true_count = -1
max_true_idx  = -1
for idx, (val, count) in enumerate(result):
    if val and max_true_count < count:
        max_true_count = count
        max_true_idx = idx

#Find total elements before and after the longest subsequence tuple
elems_before_idx = sum((idx[1] for idx in result[:max_true_idx]))
elems_after_idx = sum((idx[1] for idx in result[max_true_idx+1:]))

#Create the output list using the information
output = [(False, elems_before_idx), (True, max_true_count), (False, elems_after_idx)]
print(output)

The output will be

[(False, 3), (True, 3), (False, 1)]
于 2019-05-25T05:55:53.490 回答
1

这是一个矢量化的 -

def keep_longest_true(a):
    # Convert to array
    a = np.asarray(a)

    # Attach sentients on either sides w.r.t True
    b = np.r_[False,a,False]

    # Get indices of group shifts
    s = np.flatnonzero(b[:-1]!=b[1:])

    # Get group lengths and hence the max index group
    m = (s[1::2]-s[::2]).argmax()

    # Initialize array and assign only the largest True island as True.
    out = np.zeros_like(a)
    out[s[2*m]:s[2*m+1]] = 1
    return out

def island_info(a):
    '''' Get island tuple info
    '''

    # Attach sentients on either sides w.r.t array start and end
    b = np.r_[~a[0],a,~a[-1]]

    # Get group lengths and group start elements
    lens = np.diff(np.flatnonzero(b[:-1] != b[1:]))
    grpID = np.resize([a[0],~a[0]],len(lens))

    # zip those two info for final o/p
    return zip(grpID,lens)

样品运行 -

In [221]: a
Out[221]: [True, True, False, True, True, True, False]

In [222]: keep_longest_true(a)
Out[222]: array([False, False, False,  True,  True,  True, False])

In [223]: island_info(keep_longest_true(a))
Out[223]: [(False, 3), (True, 3), (False, 1)]
于 2019-05-25T06:19:48.233 回答