<p>Given an array of string <code>words</code>, return <em>all strings in </em><code>words</code><em> that is a <strong>substring</strong> of another word</em>. You can return the answer in <strong>any order</strong>.</p>

<p>A <strong>substring</strong> is a contiguous sequence of characters within a string</p>

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

<pre>
<strong>Input:</strong> words = [&quot;mass&quot;,&quot;as&quot;,&quot;hero&quot;,&quot;superhero&quot;]
<strong>Output:</strong> [&quot;as&quot;,&quot;hero&quot;]
<strong>Explanation:</strong> &quot;as&quot; is substring of &quot;mass&quot; and &quot;hero&quot; is substring of &quot;superhero&quot;.
[&quot;hero&quot;,&quot;as&quot;] is also a valid answer.
</pre>

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

<pre>
<strong>Input:</strong> words = [&quot;leetcode&quot;,&quot;et&quot;,&quot;code&quot;]
<strong>Output:</strong> [&quot;et&quot;,&quot;code&quot;]
<strong>Explanation:</strong> &quot;et&quot;, &quot;code&quot; are substring of &quot;leetcode&quot;.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;blue&quot;,&quot;green&quot;,&quot;bu&quot;]
<strong>Output:</strong> []
<strong>Explanation:</strong> No string of words is substring of another string.
</pre>

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

<ul>
	<li><code>1 &lt;= words.length &lt;= 100</code></li>
	<li><code>1 &lt;= words[i].length &lt;= 30</code></li>
	<li><code>words[i]</code> contains only lowercase English letters.</li>
	<li>All the strings of <code>words</code> are <strong>unique</strong>.</li>
</ul>

class Solution {
    vector<int> findlps(string &s){
        int n = s.length();
        vector<int> lps(n, 0);
        int pre = 0, suf = 1;
        while(suf < n){
            if(s[suf] == s[pre]){
                lps[suf] = pre+1;
                suf++;
                pre++;
            }
            else{
                if(pre == 0) suf++;
                else pre = lps[pre-1];
            }
        }
        return lps;
    }

    int firstOccurence(string &needle, string &haystack){
        int n = needle.length();
        int m = haystack.length();
        int i=0, j=0;
        vector<int> lps = findlps(haystack);

        while(i < n && j < m){
            if(needle[i] == haystack[j]){
                i++;
                j++;
            }
            else{
                if(j == 0) i++;
                else j = lps[j-1];
            }
        }
        if(j == m) return i-j;
        return -1;
    }

    static bool comp(string &s1, string &s2){
        return s1.length() < s2.length();
    }

public:
    vector<string> stringMatching(vector<string>& words) {
        sort(begin(words), end(words), comp);
        vector<string> v;

        for(int i=0; i<words.size(); i++){
            string haystack = words[i];
            for(int j=i+1; j<words.size(); j++){
                string needle = words[j];
                if(firstOccurence(needle, haystack) != -1){
                    v.push_back(haystack);
                    break;
                }
            }
        }
        return v;
    }
};
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