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

        unordered_set<int> visited;
        int groups = hand.size() / groupSize;

        int minStart = 0;
        bool minStartSet;
        int count, prev, j;
        for (int i = 0; i < groups; ++i) {
            minStartSet = false;
            count = 1;
            prev = hand[minStart];
            visited.insert(minStart);
            for (j = minStart + 1; j < hand.size() && count < groupSize; ++j) {
                if (hand[j] != prev + 1 || visited.find(j) != visited.end()) {
                    if (!minStartSet && visited.find(j) == visited.end()) {
                        minStart = j;
                        minStartSet = true;
                    }
                    continue;
                }
                else {
                    prev = hand[j];
                    visited.insert(j);
                    count++;
                }
            }
            if (!minStartSet && visited.find(j) == visited.end() && j != hand.size()) {
                minStart = j;
            }
            if (count != groupSize) {
                return false;
            }
        }

        return true;
    }
};
27995