Took Microsoft OA yesterday: 2 coding and 10 MCQ

1. Maximum possible value by inserting '5'
   examples:
   input: 1234 -> output: 51234
   input: 7643 -> output 76543
   input: 0 -> output 50
   input: -661 -> output -5661

2. A string is considered balanced when every letter in the string appears both in uppercase and lowercase
   For example, CATattac is balanced (a, c, t occur in both cases). Madam is not (a, d only appear in lowercase).
   Write a function that given a string returns the shortest balanced substring of that string.
   Can this be solved with a sliding window approach?
   Update:
   More examples
   “azABaabza” returns “ABaab”
   “TacoCat” returns -1 (not balanced)
   “AcZCbaBz” returns the entire string

3. MCQs mostly on the time complexity and theory.

Ques 1 is straight forward but Ques 2 took a lot of time :(