0686. Repeated String Match

https://leetcode.com/problems/repeated-string-match

Description

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 "ab**cdabcdab**cd", 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 <= 104

• 1 <= b.length <= 104

• a and b consist of lower-case English letters.

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