clean & easy solution using hashmap ✅ | | faster than 95.89% in runtime  🔥🔥🔥
\n# Code\n\nclass Solution:\n    def maximumSum(self, arr: List[int]) -> int:\n        hashmap = defaultdict(list)\n        for n in arr:\n            digit_sum
\n# Code\n```\nclass Solution:\n    def maximumSum(self, arr: List[int]) -> int:\n        hashmap = defaultdict(list)\n        for n in arr:\n            digit_sum = 0\n            num = n\n            while num:\n                digit_sum += num % 10\n                num //= 10\n            hashmap[digit_sum].append(n)\n\n        ans = -1\n        for v in hashmap.values():\n            if len(v) > 1:\n                v = sorted(v,reverse=True)\n                ans = max(ans, v[0] + v[1])\n        return ans \n```
['Hash Table', 'Sorting', 'Python3']