Rabbits in Forest
<p>There is a forest with an unknown number of rabbits. We asked n rabbits <strong>&quot;How many rabbits have the same color as you?&quot;</strong> and collected the answers in an integer array <code>answers</code> where <code>answers[i]</code> is the answer of the <code>i<sup>th</sup></code> rabbit.</p>

<p>Given the array <code>answers</code>, return <em>the minimum number of rabbits that could be in the forest</em>.</p>

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

<pre>
<strong>Input:</strong> answers = [1,1,2]
<strong>Output:</strong> 5
<strong>Explanation:</strong>
The two rabbits that answered &quot;1&quot; could both be the same color, say red.
The rabbit that answered &quot;2&quot; can&#39;t be red or the answers would be inconsistent.
Say the rabbit that answered &quot;2&quot; was blue.
Then there should be 2 other blue rabbits in the forest that didn&#39;t answer into the array.
The smallest possible number of rabbits in the forest is therefore 5: 3 that answered plus 2 that didn&#39;t.
</pre>

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

<pre>
<strong>Input:</strong> answers = [10,10,10]
<strong>Output:</strong> 11
</pre>

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

<ul>
	<li><code>1 &lt;= answers.length &lt;= 1000</code></li>
	<li><code>0 &lt;= answers[i] &lt; 1000</code></li>
</ul>
Greedy; Array; Hash Table; Math
class Solution {
public:
    int numRabbits(vector<int>& answers) {
        unordered_map<int, int> cnt;
        for (int x : answers) {
            ++cnt[x];
        }
        int ans = 0;
        for (auto& [x, v] : cnt) {
            int group = x + 1;
            ans += (v + group - 1) / group * group;
        }
        return ans;
    }
};
