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

def minimum_window(s, t, min_length = 100000):
    d = {}
    for x in t:
        if x in d:
            d[x]+= 1
        else:
            d[x] = 1

    tot = sum([y for x,y in d.iteritems()])
    l = []
    ind = 0 
    for i,x in enumerate(s):
        if ind == 1:
            l = l + [x]
        if x in d:
            tot-=1
            if not l:
                ind = 1
                l = [x]

        if tot == 0:
            if len(l)