686. 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 "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.

# @lc code=start
using LeetCode

function repeated_string_match(a::String, b::String)
    minres = (length(b) - 1) ÷ length(a) + 1
    s = a ^ minres
    for i in 0:2
        occursin(b, s) && return minres + i
        s *= a
    end
    return -1
end
# @lc code=end

repeated_string_match (generic function with 1 method)

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