CODEWITHSUNDEEP
pythonlist
Nilani Algiriyage
Nilani Algiriyage

Reputation: 35646

Python traverse through list and count items based on conditions

Lets say I have a Python list like following.

list2 = list('ABCDCBEGHGWAOUOV')
['A', 'B', 'C', 'D', 'C', 'B', 'E', 'G', 'H', 'G', 'W', 'A', 'O', 'U', 'O', 'V']

While traversing the list at the 5th point I see 'C' is occurring again. So up to 'D' it is +4 and and the -1 since it come back.

A->B->C->D +3
C<-D -1
B<-C -1
B->E->G->H +3
G<-H -1
G->W +1
A<-W -4 etc...

I need to count steps for forward as positive and backward as negative. Any help for implementing this?

list1 = []
for item in list2:
    if item in list1:
        sum(1 for i in list2)
    else:
        list1.append(item)

Upvotes: 0

Views: 84

Answers (1)

freakish
freakish

Reputation: 56467

I'm not sure what's the expected output or what's the rule behind these numbers. This doesn't make much sens: A<-W -4. And this: A->B->C->D +4: do you count nodes? But here C<-D -1 you count "steps", i.e. arrows? Anyway I'll give it a shot since it looks like a funny thing:

from itertools import islice

def get_it(list2):
    moves = []
    buffer = []
    prev = list2[0]

    for current in islice(list2, 1, None):
        el = 2 * (current > prev) - 1
        if buffer and el != buffer[0]:
            moves.append(sum(buffer))
            buffer = []
        buffer.append(el)
        prev = current

    if buffer:
        moves.append(sum(buffer))

    return moves

Upvotes: 1

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