<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:

    void create_lps(vector<int> &lps, string s)
    {
        int pre=0,suff=1;
	    int n=s.length();
	    while(suff<n)
	    {
	        if(s[pre]==s[suff])
	        {
	            lps[suff]= pre+1;
	            pre++;
	            suff++;
	        }else
	        {
	            if(pre==0) 
	            {
	                lps[suff]=0;
	                suff++;
	            }else
	            {
	                pre= lps[pre-1];
	            }
	        }
	    }
    }

    int strStr(string haystack, string needle) {
        vector<int> lps(needle.size(),0);
        create_lps(lps,needle);

        int first=0, second=0;
        while(first<haystack.length() && second<needle.length())
        {
            if(haystack[first]== needle[second])
            {
                first++;
                second++;
            }else
            {
                if(second==0)
                {
                    first++;
                }else{
                    second= lps[second-1];
                }
            }
        }
        if(second==needle.length())
        {
            return 1;
        }else
        {
            return -1;
        }
    }


    int repeatedStringMatch(string a, string b) {
        
        if(a==b) return 1;
        
        string temp=a;
        int cnt=1;

        while(temp.size()<b.size())
        {
            cnt++;
            temp= temp+ a;
        }
        if(strStr(temp, b) == 1) return cnt;
        
        cnt++;
        temp= temp+a;
        int final_check=  strStr(temp,b);
        if(final_check==1) return cnt;
        else return -1;
        
    }
};
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