[Python] Rearranging pairs in an array into subarrays with adjacent pairs having the same...

Hi I have a problem with the following numpy array for example:

a = np.array([[1,2],[2,4],[5,6],[3,4],[7,8],[3,5]])



And I need an output array to be:

[np.array([1,2,2,4,4,3,3,5,5,6]),
np.array([7,8])]


Although the elements in the subarrays and array don't have to be in order.

Pairs should be flipped if they can be part of the subarray in the output. The pairs are guaranteed to have non identical elements.

My crude attempt is below, but it doesn't give the correct output.

import numpy as np
def concatenate_neighbouring_pairs(input):
output = []
for i in range(len(input)):
subarray = input

for j in range(1,len(input)):
#print(i,j)
intersect1 = np.in1d(subarray, input[j])
intersect2 = np.in1d(input[j] ,subarray)
#print(intersect1, intersect2)

if intersect1[0] == True and intersect1[-1] == False and intersect2[0] == True and intersect2[-1] == False:
subarray = np.concatenate((np.flip(input[j]),subarray))

elif intersect1[0] == True and intersect1[-1] == False and intersect2[0] == False and intersect2[-1] == True:
subarray = np.concatenate((input[j], subarray))

elif intersect1[0] == False and intersect1[-1] == True and intersect2[0] == True and intersect2[-1] == False:
subarray = np.concatenate((subarray, input[j]))

elif intersect1[0] == False and intersect1[-1] == True and intersect2[0] == False and intersect2[-1] == True:
subarray = np.concatenate((subarray, np.flip(input[j])))



output.append(subarray)
return output


Calling the function outputs:

[array([1, 2, 2, 4, 4, 3, 3, 5]),
array([2, 4, 4, 3, 3, 5]),
array([3, 5, 5, 6]),
array([5, 3, 3, 4, 4, 2]),
array([7, 8]),
array([4, 3, 3, 5, 5, 6])]

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