Repeated String Match

Problem 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 "abcdabcdabcd", b is a substring of it.

Example 2:

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

Constraints:

• 1 <= a.length, b.length <= 104
• a and b consist of lowercase English letters.

Solution (JavaScript)

/**
 * @param {string} A
 * @param {string} B
 * @return {number}
 */
var repeatedStringMatch = function(A, B) {
    let num = 1, s = A;
    while(s.length < B.length){
            s += A;
            num++;
    }
    
    if(s.includes(B)) return num;
    if((s+A).includes(B)) return num+1;
    return -1;
};