<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 {
private:
    bool KMP(string s, string p) {
        int n = p.size();
        int m = s.size();

        vector<int> LPS(n, 0);
        int i = 0, j = 1;
        while(j < n) {
            if(p[i] == p[j]) {
                LPS[j] = i+1;
                i++, j++;
            }
            else {
                if(i == 0) j++;
                else i = LPS[i-1];
            }
        }

        i = 0, j = 0;
        while(i < s.size()) {
            if(s[i] == p[j]) {
                i++, j++;
            }
            if(j == n) return true;
            if(i < m && s[i] != p[j]) {
                if(j == 0) i++;
                else j = LPS[j-1];
            }
        }
        return false;
    }

public:
    vector<string> stringMatching(vector<string>& words) {
        int n = words.size();
        vector<string> ans;
        set<int> st;
        for(int i = 0; i < n; i++) {
            for(int j = 0; j < n; j++) {
                if(i == j || words[i].size() < words[j].size()) continue;
                else {
                    if(KMP(words[i], words[j])) st.insert(j);
                }
            }
        }
        for(auto it: st) {
            ans.push_back(words[it]);
        }
        return ans;
    }
};
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