846. Hand of Straights

846. Hand of Straights

Medium

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

Given an integer array hand where hand[i] is the value written on the ith card and an integer groupSize, return true if she can rearrange the cards, or false otherwise.

Example 1:

• Input: hand = [1,2,3,6,2,3,4,7,8], groupSize = 3
• Output: true
• Explanation: Alice's hand can be rearranged as [1,2,3],[2,3,4],[6,7,8]

Example 2:

• Input: hand = [1,2,3,4,5], groupSize = 4
• Output: false
• Explanation: Alice's hand can not be rearranged into groups of 4.

Example 3:

• Input: hand = [2,1], groupSize = 2
• Output: true
• Explanation: Alice's hand can not be rearranged into groups of 2.

Constraints:

• 1 <= hand.length <= 104
• 0 <= hand[i] <= 109
• 1 <= groupSize <= hand.length

Note: This question is the same as 1296: https://leetcode.com/problems/divide-array-in-sets-of-k-consecutive-numbers/

Solution:

class Solution {

    /**
     * @param Integer[] $hand
     * @param Integer $groupSize
     * @return Boolean
     */
    function isNStraightHand($hand, $groupSize) {
        $cardCounts = array();
        foreach ($hand as $card) {
            if (!isset($cardCounts[$card])) {
                $cardCounts[$card] = 1;
            } else {
                $cardCounts[$card]++;
            }
        }
        sort($hand);
        foreach ($hand as $card) {
            if (isset($cardCounts[$card])) {
                for ($nextCard = $card; $nextCard < $card + $groupSize; $nextCard++) {
                    if (!isset($cardCounts[$nextCard])) {
                        return false;
                    }
                    if (--$cardCounts[$nextCard] == 0) {
                        unset($cardCounts[$nextCard]);
                    }
                }
            }
        }
        return true;
    }
}

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