Substring Concatenation

You are given a string, S, and a list of words, L, that are all of the same length.

Find all starting indices of substring(s) in S that is a concatenation of each word in L exactly once and without any intervening characters.

Example :

S: "barfoothefoobarman"
L: ["foo", "bar"]

You should return the indices: [0,9].
(order does not matter).

NOTE: You only need to implement the given function. Do not read input, instead use the arguments to the function. Do not print the output, instead return values as specified. Still have a question? Checkout Sample Codes for more details.