<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) {
        int n = hand.size();

        if(n % groupSize)   return false;
        int groups = n / groupSize;

        sort(hand.begin(), hand.end());

        vector<set<int>> container(groups);
        container[0].insert(hand[0]);

        int prev = 0;
        for(int i = 1; i < n; i++) {
            if(hand[i-1] == hand[i]) {
                prev = (prev + 1) % groups;
                container[prev].insert(hand[i]);
            }
            else {
                for(int j = 0; j < groups; j++) {
                    if(container[j].size() < groupSize) {
                        container[j].insert(hand[i]);
                        // prev = (prev + 1) % groups;
                        prev = j;
                        break;
                    }
                }
            }
        }

        for(int i = 0; i < groups; i++) {
            // cout << i << " => ";
            // for(auto it: container[i]) cout << it << " ";
            // cout << endl;

            int diff = abs(*container[i].rbegin() - *container[i].begin());

            // cout << (*container[i].rbegin()) << "##" << (*container[i].begin()) << " ";
            // cout << diff << endl << (diff != (groupSize - 1)) << endl;
            
            if(diff != (groupSize - 1) || container[i].size() != groupSize) return false;
        }

        return true;
    }
};
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