<p>The <strong>DNA sequence</strong> is composed of a series of nucleotides abbreviated as <code>&#39;A&#39;</code>, <code>&#39;C&#39;</code>, <code>&#39;G&#39;</code>, and <code>&#39;T&#39;</code>.</p>

<ul>
	<li>For example, <code>&quot;ACGAATTCCG&quot;</code> is a <strong>DNA sequence</strong>.</li>
</ul>

<p>When studying <strong>DNA</strong>, it is useful to identify repeated sequences within the DNA.</p>

<p>Given a string <code>s</code> that represents a <strong>DNA sequence</strong>, return all the <strong><code>10</code>-letter-long</strong> sequences (substrings) that occur more than once in a DNA molecule. You may return the answer in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT"
<strong>Output:</strong> ["AAAAACCCCC","CCCCCAAAAA"]
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> s = "AAAAAAAAAAAAA"
<strong>Output:</strong> ["AAAAAAAAAA"]
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
	<li><code>s[i]</code> is either <code>&#39;A&#39;</code>, <code>&#39;C&#39;</code>, <code>&#39;G&#39;</code>, or <code>&#39;T&#39;</code>.</li>
</ul>

class Solution {
public:
    const int p = 7, M = 1e9 + 9;
    vector<string> findRepeatedDnaSequences(string s) {
        long long n = s.size(), hash[n], p_pow[n];
        hash[0] = s[0] - 'A' + 1; p_pow[0] = 1;
        for (int i = 1; i < n; i++) {
            hash[i] = (hash[i - 1] * p % M + s[i] - 'A' + 1) % M;
            p_pow[i] = p_pow[i - 1] * p % M;
        }

        auto sub_hash = [&] (int l, int r) {
            if (!l) return hash[r];
            else return ((hash[r] - hash[l - 1] * p_pow[r - l + 1]) % M + M) % M;
        };

        map<long long, int> mpp; vector<string> res;
        for (int i = 0; i < n - 9; i++) {
            int x = sub_hash(i, i + 9);
            if(mpp[x] == 1) res.push_back(s.substr(i, 10));
            mpp[x]++;
        }
        return res;       
    }
};
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