<p>Given an array of strings <code>strs</code>, group the <span data-keyword="anagram">anagrams</span> together. You can return the answer in <strong>any order</strong>.</p>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">strs = [&quot;eat&quot;,&quot;tea&quot;,&quot;tan&quot;,&quot;ate&quot;,&quot;nat&quot;,&quot;bat&quot;]</span></p>

<p><strong>Output:</strong> <span class="example-io">[[&quot;bat&quot;],[&quot;nat&quot;,&quot;tan&quot;],[&quot;ate&quot;,&quot;eat&quot;,&quot;tea&quot;]]</span></p>

<p><strong>Explanation:</strong></p>

<ul>
	<li>There is no string in strs that can be rearranged to form <code>&quot;bat&quot;</code>.</li>
	<li>The strings <code>&quot;nat&quot;</code> and <code>&quot;tan&quot;</code> are anagrams as they can be rearranged to form each other.</li>
	<li>The strings <code>&quot;ate&quot;</code>, <code>&quot;eat&quot;</code>, and <code>&quot;tea&quot;</code> are anagrams as they can be rearranged to form each other.</li>
</ul>
</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">strs = [&quot;&quot;]</span></p>

<p><strong>Output:</strong> <span class="example-io">[[&quot;&quot;]]</span></p>
</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">strs = [&quot;a&quot;]</span></p>

<p><strong>Output:</strong> <span class="example-io">[[&quot;a&quot;]]</span></p>
</div>

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

<ul>
	<li><code>1 &lt;= strs.length &lt;= 10<sup>4</sup></code></li>
	<li><code>0 &lt;= strs[i].length &lt;= 100</code></li>
	<li><code>strs[i]</code> consists of lowercase English letters.</li>
</ul>

class Solution {
public:
    vector<vector<string>> groupAnagrams(vector<string>& strs) {
        map<long long, vector<string>> groups;
        int hast_arr[26] = {643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821};
        for (auto &word : strs) {
            long long hash = 1;
            for (auto &chr : word){
                hash *= hast_arr[chr -'a'];
                hash %= 1000000007;
            }
            auto find = groups.find(hash);
            if (find == groups.end()){
                groups[hash] = {word};
            }else{
                groups[hash].push_back(word);
            }
        }
        vector<vector<string>> retval(groups.size());
        int i = 0;
        for (auto &group : groups){
            retval[i++] = move(group.second);
        }
        return retval;
    }
};
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