m0686.py

"""Repeated String Match
Given two strings a and b, return the minimum number of times you should repeat
string a so that string b is a substring of it. If it is impossible for b to be
a substring of a after repeating it, return -1.

Notice: string "abc" repeated 0 times is "",  repeated 1 time is "abc" and
repeated 2 times is "abcabc".

Example 1:

* Input: a = "abcd", b = "cdabcdab"
* Output: 3
* Explanation: We return 3 because by repeating a three times "abcdabcdabcd", b
  is a substring of it.

Example 2:

* Input: a = "a", b = "aa"
* Output: 2

Example 3:

* Input: a = "a", b = "a"
* Output: 1

Example 4:

* Input: a = "abc", b = "wxyz"
* Output: -1

Constraints:

* 1 <= a.length <= 10^4
* 1 <= b.length <= 10^4
* a and b consist of lower-case English letters.
"""