2025-08-21 14:05:33 +0000 UTC

class Solution:
    def isGood(self, nums: list[int]) -> bool:
        mx = max(nums)
        if len(nums) != mx + 1:
            return False
        freqs = defaultdict(int)
        for num in nums:
            freqs[num] += 1
        if freqs[mx] != 2:
            return False
        for i in range(1, mx):
            if freqs[i] != 1:
                return False
        return True