Hackerrank All Women's Codesprint 2019: Name the Product Link: https://www.hackerrank.com/contests/hackerrank-all-womens-codesprint-2019/challenges/name-the-product/    

Problem


  You are contesting to name a new product in your company given the following conditions:
  
  You are given an array of \$n\$ different names, \$names\$, where \$names_i\$ denotes the \$i^{th}\$ name and all the names are of length \$5\$. The distance between any two names is the number of positions in which the characters in these names differ. For example, "bubby" and "bunny" differ in two positions.
  
  You have to choose a name such that the sum of differences of all names in \$names\$ with the chosen name is maximal. In order to win the contest, give the new product this chosen name.
  
  Note: If there are many such names chose the lexicographically largest one.
  
  Take for example, names = ["bubby", "bunny", "berry"], with length \$n = 3\$. Then, the name that you should choose is "zzzzz" as this name has no common character with any name in the names list and is also lexicographically the largest.
  
  Function Description
  
  Complete the productName function in the editor below. It should return the lexigraphically largest string of length  whose sum of differences with all the names is maximal.
  
  productName has the following parameter(s):
  
  names: array of \$n\$ names
  
  Input Format
  
  
  The first line contains an integer, \$n\$, denoting the number of elements in \$names\$.
  Each line \$i\$ of the \$n\$ subsequent lines (where \$0 \le i \le n\$) contains a string describing \$names_i\$.
  
  
  Constraints
  
  
  \$1 \le n \le 10^5\$
  All characters in the names are lowercase English alphabets.
  Each name is of length \$5\$.
  
  
  Output Format
  
  
  The output should contain the lexigraphically largest string of length  whose sum of differences with all the names is maximal.
  
  
  Sample Input 0

3
bubby
bunny
berry

  
  Sample Output 0

zzzzz

  
  Explanation 0
  
  
  Difference between \$names_0\$, bubby, and zzzzz is \$5\$.
  Difference between \$names_1\$, bunny, and zzzzz is \$5\$.
  Difference between \$names_2\$, berry, and zzzzz is \$5\$.
  So, total difference is 15, which is maximal.
  
  
  Sample Input 1

3
ready
stedy
zebra

  
  Sample Output 1

yzzzz

  
  Explanation 1
  
  
  Difference between \$names_0\$, ready, and yzzzz is \$5\$.
  Difference between \$names_1\$, stedy, and yzzzz is \$5\$.
  Difference between \$names_2\$, zebra, and yzzzz is \$5\$.
  So, total differce is 15, which is maximal.
  
  
  


I would strip the extraneous parts from my solution:   

import math, os, random, re, sys
from collections import defaultdict as dd, Counter as count

alphabet = "abcdefghijklmnopqrstuvwxyz"
def productName(names):
    charmap = [dd(lambda: 0, count(name[i] for name in names)) for i in range(5)]
    return "".join(max(alphabet, key=lambda x: (-charmap[i][x], x)) for i in range(5))   


I'm concerned with adhering to best practices and maximising performance.
Imports
import math, os, random, re, sys
from collections import defaultdict as dd, Counter as count

Seriously, don't do this. It may be useful to read PEP8 regarding imports again.

Imports should be on separate lines.

Why do Counter as count?  It impairs readability.
Especially in larger scripts, every Python dev knows Counter, but count could be a random variable and is easy to be overshadowed.

You don't use all of the imported modules; just remove them if you don't need them.


   alphabet = &quot;abcdefghijklmnopqrstuvwxyz&quot;

Here you missed something that is in the standard lib: from string import ascii_lowercase


Misc

This dd(lambda: 0, ... adds no value
Counter is already a dictionary with default value 0 just remove that part

Magic numbers
5 is a Magic number, you should define it as a CONSTANT:
  NAME_LENGTH = 5



The rest looks good!