<p>Given two strings <code>a</code> and <code>b</code>, return <em>the minimum number of times you should repeat string </em><code>a</code><em> so that string</em> <code>b</code> <em>is a substring of it</em>. If it is impossible for <code>b</code>​​​​​​ to be a substring of <code>a</code> after repeating it, return <code>-1</code>.</p>

<p><strong>Notice:</strong> string <code>&quot;abc&quot;</code> repeated 0 times is <code>&quot;&quot;</code>, repeated 1 time is <code>&quot;abc&quot;</code> and repeated 2 times is <code>&quot;abcabc&quot;</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> a = &quot;abcd&quot;, b = &quot;cdabcdab&quot;
<strong>Output:</strong> 3
<strong>Explanation:</strong> We return 3 because by repeating a three times &quot;ab<strong>cdabcdab</strong>cd&quot;, b is a substring of it.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> a = &quot;a&quot;, b = &quot;aa&quot;
<strong>Output:</strong> 2
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= a.length, b.length &lt;= 10<sup>4</sup></code></li>
	<li><code>a</code> and <code>b</code> consist of lowercase English letters.</li>
</ul>

class Solution {
public:
    bool checkEachChar(string a, string b) {
        for (int i = 0; i < a.size(); i++) {
            if (a[i] != b[i]) {
                return false;
            }
        }
        return true;
    }
    bool patternMatching(string a, string b) {
        int n = a.size();
        int m = b.size();
        long long bHashValue = 0;
        long long power_ten = 1;
        for (int j = 0; j < m; j++) {
            bHashValue += b[j] * power_ten;
            // power_ten *= 3;
        }
        for (int i = 0; i <= n - m; i++) {
            long long currentHashValue = 0;
            int power_ten = 1;
            for (int j = i; j < i+m; j++) {
                currentHashValue += a[j] * power_ten;
                // power_ten *= 3;
            }
            if (currentHashValue == bHashValue) {
                bool ifEachMatched = checkEachChar(a.substr(i, m), b);
                if (ifEachMatched) {
                    return true;
                }
            }
        }
        return false;
    }
    int repeatedStringMatch(string a, string b) {
        string a_transformed = "";
        if (b == "" || a == "") {
            return 0;
        }
        int minrepeat = b.size() / a.size();
        for (int i = 0; i < minrepeat; i++) {
            a_transformed += a;
        }
        if (patternMatching(a_transformed, b) != false) {
            return minrepeat;
        }
        a_transformed += a;

        if (patternMatching(a_transformed, b) != false) {
            return minrepeat + 1;
        }
        a_transformed += a;
        if (patternMatching(a_transformed, b) != false) {
            return minrepeat + 2;
        }
        return -1;
    }
};
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