String from an array of words

Problem statement

You are given an array of strings arr. Your task is to construct a string from the words in arr starting with the 0^th character from each word (in the order they appear in arr), followed by the 1^th character, then the 2^th character, etc. If one of the words doesn’t have an i^th character, skip that word.

Return the resulting string.

Examples

Example 1

For arr = [“Daisy”, “Rose”, “Hyacinth”, “Poppy”], the output should be solution(arr) = “DRHPaoyoisapsecpyiynth”

• First, we append all 0^th characters and obtain string “DRHP”
• Then we append all 1^th characters and obtain string “DRHPaoyo”
• Then we append all 2^th characters and obtain string “DRHPaoyoisap”
• Then we append all 3^rd characters and obtain string “DRHPaoyoisapaecp”
• Then we append all 4^th characters and obtain string “DRHPaoyoisapaecpyiy”
• Finally, only letters in the arr[2] are left, so we append the rest characters and get “DRHPaoyoisapaecpyiynth”

Example 2

For arr = [“E”, “M”, “I”, “L”, “Y”] the output should be solution(arr) = “EMILY”

• Since each of these strings have only one character, the answer will be concatenation of each string in order, so the answer is EMILY

Input/Output

Guaranteed constraints:
1 ≤ arr.length ≤ 100
1 ≤ arr[i].length < 100

[execution time limit] 4 seconds (py3)

[input] array string arr

An array of strings containing alphanumeric characters.

[output] string

Return the resulting string.

Implementation

def helper(arr, i, temp=""):
    for word in arr:
        if i < len(word):
            temp += word[i]
        else:
            continue
    return temp

def solution(arr):
    result_string = ""
    i = 0
    max_len = 0

    for word in arr:
        if len(word) > max_len:
            max_len = len(word)
    
    for wrd in arr:
        while i<max_len:
            result_string += helper(arr,i)
            i += 1
    
    return result_string