<p>You are given an integer array <code>arr</code>. You can choose a set of integers and remove all the occurrences of these integers in the array.</p>

<p>Return <em>the minimum size of the set so that <strong>at least</strong> half of the integers of the array are removed</em>.</p>

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

<pre>
<strong>Input:</strong> arr = [3,3,3,3,5,5,5,2,2,7]
<strong>Output:</strong> 2
<strong>Explanation:</strong> Choosing {3,7} will make the new array [5,5,5,2,2] which has size 5 (i.e equal to half of the size of the old array).
Possible sets of size 2 are {3,5},{3,2},{5,2}.
Choosing set {2,7} is not possible as it will make the new array [3,3,3,3,5,5,5] which has a size greater than half of the size of the old array.
</pre>

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

<pre>
<strong>Input:</strong> arr = [7,7,7,7,7,7]
<strong>Output:</strong> 1
<strong>Explanation:</strong> The only possible set you can choose is {7}. This will make the new array empty.
</pre>

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

<ul>
	<li><code>2 &lt;= arr.length &lt;= 10<sup>5</sup></code></li>
	<li><code>arr.length</code> is even.</li>
	<li><code>1 &lt;= arr[i] &lt;= 10<sup>5</sup></code></li>
</ul>

#pragma GCC optimize ("O3,unroll-loops")
#pragma GCC target ("avx2,bmi,bmi2,lzcnt,popcnt")

#define pii pair<int,int>

class Solution {
public:
    int minSetSize(vector<int>& arr) {
        ios_base::sync_with_stdio(false);
        cin.tie(0);

        vector<int> counts (*max_element(arr.begin(),arr.end())+1);
        for (const int &x : arr) counts[x]++;

        vector<pii> pairs;
        for (int i = 0; i < counts.size(); i++)
            if (counts[i]) pairs.push_back(pair(i,counts[i]));
        sort(pairs.begin(), pairs.end(), [] (const pii &a, const pii &b) {
            return a.second > b.second;
        });

        int len = arr.size(), currSize = 0, ans = 0;
        for (const pii &x : pairs) {
            currSize += x.second;
            ans++;
            if (currSize*2 >= len) return ans;
        }

        return 0;
    }
};
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