<p>Alice has some number of cards and she wants to rearrange the cards into groups so that each group is of size <code>groupSize</code>, and consists of <code>groupSize</code> consecutive cards.</p>

<p>Given an integer array <code>hand</code> where <code>hand[i]</code> is the value written on the <code>i<sup>th</sup></code> card and an integer <code>groupSize</code>, return <code>true</code> if she can rearrange the cards, or <code>false</code> otherwise.</p>

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

<pre>
<strong>Input:</strong> hand = [1,2,3,6,2,3,4,7,8], groupSize = 3
<strong>Output:</strong> true
<strong>Explanation:</strong> Alice&#39;s hand can be rearranged as [1,2,3],[2,3,4],[6,7,8]
</pre>

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

<pre>
<strong>Input:</strong> hand = [1,2,3,4,5], groupSize = 4
<strong>Output:</strong> false
<strong>Explanation:</strong> Alice&#39;s hand can not be rearranged into groups of 4.

</pre>

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

<ul>
	<li><code>1 &lt;= hand.length &lt;= 10<sup>4</sup></code></li>
	<li><code>0 &lt;= hand[i] &lt;= 10<sup>9</sup></code></li>
	<li><code>1 &lt;= groupSize &lt;= hand.length</code></li>
</ul>

<p>&nbsp;</p>
<p><strong>Note:</strong> This question is the same as 1296: <a href="https://leetcode.com/problems/divide-array-in-sets-of-k-consecutive-numbers/" target="_blank">https://leetcode.com/problems/divide-array-in-sets-of-k-consecutive-numbers/</a></p>

class Solution {
    public:
    bool isNStraightHand(vector<int> &hand, int groupSize) {
        if (hand.size() % groupSize != 0) {
            return false;
        }
        list<pair<int, int>> vv;
        sort(begin(hand), end(hand));
        int cur = -1;
        for (auto h : hand) {
            if (h != cur) {
                vv.push_back({ h, 1 });
                cur = h;
            } else {
                ++vv.back().second;
            }
        }

        while (!vv.empty()) {
            auto it = begin(vv);
            int v = it->first;
            if (it->second == 1) {
                it = vv.erase(it);
            } else {
                --it->second;
                ++it;
            }
            for (int i = 1; i < groupSize; ++i) {
                if (it->first != v + 1) {
                    return false;
                }
                v = it->first;
                if (it->second == 1) {
                    it = vv.erase(it);
                } else {
                    --it->second;
                    ++it;
                }
            }
        }
        return true;
    }
};
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