Return a combined string of all middle letters of list of strings-CodePudding

im trying to return all the middle letters in a string, eg, list = ["Guesss", "what", "idk"] which would return ead where if list[i] is odd it gets the middle letter and if list[i] is even it gets the second middle letter like in what the middle letters are ha and returns the second letter a.

How can I do this using recursion? - with no loops

This is what I've come up so far:

def get_middle_letters(words):
    if words == []:
        return ""
    if len(words[0]) % 2 == 1:
        middle = len(words[0]) // 2
        return (words[0][middle])   (get_middle_letters(words[1:]))
    elif len(words[0]) % 2 == 0:
        middle = len(words[0]) // 2
        return ((words[0][middle   1])   (get_middle_letters(words[1:])))

words = ['Humans', 'are', 'lazy']
print(get_middle_letters(words))
print(get_middle_letters([]), "#EMPTY")
print(get_middle_letters(['words']))

CodePudding user response：

def middle_letters(words):
    if len(words) == 0:
        return ""
    else:
        return words[0][len(words[0])//2]   middle_letters(words[1:])

print(middle_letters(["Guesss", "what", "idk"])) # sad

The answer should be 'sad' according to your logic.

CodePudding user response：

'lazy' has four characters, so the middle == 2.

'lazy'[2 1] == 'y', but you wanted z, which is at index 2.

You don't need the 1.

That being said, you don't need to check even/odd at all. Your odd length strings already work.

CodePudding user response：

A possible recursive approach:

def middle_letters(words: list):
    # base case
    if not words:
        return ''
    # recursive case
    last = words.pop()
    return middle_letters(words)   last[len(last) // 2]

Behold, the power of a one-liner:

def middle_letters(words: list):
    return (middle_letters(words[:-1])   words[-1][len(words[-1]) // 2]) if words else ''

Test

print(repr(middle_letters([])))
print(repr(middle_letters(['Humans', 'are', 'lazy'])))
print(repr(middle_letters(["Guesss", "what", "idk"])))

Out[1]:

''
'arz'
'sad'