## The challenge#

There is an array of strings. All strings contain similar letters except one. Try to find it!

``````find_uniq([ 'Aa', 'aaa', 'aaaaa', 'BbBb', 'Aaaa', 'AaAaAa', 'a' ]) # => 'BbBb'
find_uniq([ 'abc', 'acb', 'bac', 'foo', 'bca', 'cab', 'cba' ]) # => 'foo'
``````

Strings may contain spaces. Spaces are not significant, only non-spaces symbols matter.
E.g. A string that contains only spaces is like an empty string.

It’s guaranteed that the array contains more than 3 strings.

## The solution in Python code#

Option 1:

``````def find_uniq(arr):
arr.sort(key=lambda x: x.lower())
arr1 = [set(i.lower()) for i in arr]
return arr if arr1.count(arr1) == 1 and str(arr1) != 'set()' else arr[-1]
``````

Option 2:

``````def find_uniq(arr):
for word in set(arr):
for letter in set(word):
if sum([1 if letter in w else 0 for w in arr]) == 1:
return word
else: continue
``````

Option 3:

``````from collections import Counter
def find_uniq(arr):
res = Counter(''.join(arr)).most_common()
return ''.join([x for x in arr if res[-1] in x])
``````

## Test cases to validate our solution#

``````test.describe('should handle sample cases')
test.assert_equals(find_uniq([ 'Aa', 'aaa', 'aaaaa', 'BbBb', 'Aaaa', 'AaAaAa', 'a' ]), 'BbBb')
test.assert_equals(find_uniq([ 'abc', 'acb', 'bac', 'foo', 'bca', 'cab', 'cba' ]), 'foo')
test.assert_equals(find_uniq([ '    ', 'a', '  ' ]), 'a')
``````