0846-hand-of-straights.java

class Solution {

    public boolean isNStraightHand(int[] hand, int groupSize) {
        if (hand.length % groupSize != 0) return false;

        HashMap<Integer, Integer> hm = new HashMap<>();
        for (int card : hand) hm.put(card, hm.getOrDefault(card, 0) + 1);

        Arrays.sort(hand);
        for (int card : hand) {
            if (hm.get(card) <= 0) continue;
            for (int i = 1; i < groupSize; i++) {
                int count = hm.getOrDefault(card + i, 0);
                if (count > 0) hm.put(card + i, count - 1); else return false;
            }
            hm.put(card, hm.get(card) - 1);
        }

        return true;
    }
}