LeetCode 846: Hand Of Straights — Step-by-Step Visual Trace

#leetcode #python #algorithms

Medium — Hash Table | Greedy | Sorting | Counting

The Problem

Determine if you can rearrange a hand of cards into groups where each group has exactly W cards forming consecutive sequences.

Approach

Use a counter to track card frequencies, then iterate through sorted cards and greedily form consecutive groups by checking if the next W consecutive cards are available. Decrement the counter for each card used in a group.

Time: O(n log n) · Space: O(n)

Code

from collections import Counter

class Solution:
    def isNStraightHand(self, hand: List[int], W: int) -> bool:
        if len(hand) % W != 0:
            return False

        counter = Counter(hand)
        hand.sort()

        for card in hand:
            if counter[card] > 0:
                for i in range(W):
                    if counter[card + i] <= 0:
                        return False
                    counter[card + i] -= 1

        return True