PeterMikel PeterMikel - 2 days ago 5
Python Question

extracting sub-sequence of integers

As of now I have this piece of code which works by extracting a sub sequence of integers which go in ascending order by the largest length

def sequence(n):

longSeq = []
curSeq = []

for i in range( len(n) ):
if i < len(n) - 1 and n[i] <= n[i+1]:
curSeq.append(n[i])

else:
curSeq.append(n[i])

if len(curSeq) > len(longSeq):

longSeq = curSeq
curSeq = []

print ('Longest sub-sequence of maxiumum length of integers is: ', longSeq)


sequence([1,2,4,1,2,3,2,4,7,8,10,12,1,3,4,5,6,7])


However when I have two sub-sequences of ascending order which are the same length it will only print out 1, how to I change this so if there are two sub-sequences of the same length it will print out both? Any help is appreciated

So when I run it I get

Longest sub-sequence of maximum length of integers is: [2, 4, 7, 8, 10, 12]

Answer

Have a loop that finds all sequences, keep track of the length of the longest sequence, then return all sequences of that length.

def long_sequences(n):
    long_sequences = []
    cur_sequence = []
    longest_sequence = 0
    for ind, val in enumerate(n):
        cur_sequence.append(val)
        if ind < len(n)-1 and val >= n[ind+1]:
            long_sequences.append(cur_sequence)
            longest_sequence = max(longest_sequence, len(cur_sequence))
            cur_sequence = []
    long_sequences.append(cur_sequence)  # to grab last one
    longest_sequence = max(longest_sequence, len(cur_sequence))
    return [seq for seq in long_sequences if len(seq) == longest_sequence]

>>> long_sequences([1,2,4,1,2,3,2,4,7,8,10,12,1,3,4,5,6,7])
[[2, 4, 7, 8, 10, 12], [1, 3, 4, 5, 6, 7]]
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