<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 != 0) return false;
        int indexOfGroup = 0;
        vector<int> group(groupSize);
        int start = 0;
        sort(hand.begin(), hand.end());
        while(true)
        {
            indexOfGroup = 0;
            int flag = 0;
            for(int i = start; i < n; i++) // loop in hand array
            {
                if(hand[i] == -1) continue;
                if(indexOfGroup == 0 || hand[i] - group[indexOfGroup-1] == 1)
                {
                    group[indexOfGroup++] = hand[i];
                    hand[i] = -1;
                }
                else
                {
                    if(!flag)
                    {
                        flag = 1;
                        start = i;
                    }
                    if(hand[i] - group[indexOfGroup-1] > 1 ) return false;
                }
                if(indexOfGroup == groupSize)
                { 
                    if(!flag) start = i + 1;
                    break;
                }     
            }
            if(start == n - 1 && groupSize != 1) return false;
            if(hand[n - 1] == -1) break;
        }
        for(int i = 0; i < n; i++)
            if(hand[i]!=-1) return false;
        return true;

    }
};
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