How to find smallest substring which contains all characters from a given string?

Question

I have recently come across an interesting question on strings. Suppose you are given following:

Input string1: \"this is a test string\"
Input strin         


        

Answer 1

JavaScript solution in bruteforce way:

function shortestSubStringOfUniqueChars(s){
	var uniqueArr = [];
	for(let i=0; i