Python O(n) space and O(n) time
\nclass Solution:\n    def largestWordCount(self, messages: List[str], senders: List[str]) -> str:\n        count_by_sender = Counter()\n        max_messages = 
```\nclass Solution:\n    def largestWordCount(self, messages: List[str], senders: List[str]) -> str:\n        count_by_sender = Counter()\n        max_messages = 0\n        for message, sender in zip(messages, senders):\n            word_count = len(message.split(" "))\n            count_by_sender[sender] += word_count\n            max_messages = max(max_messages, count_by_sender[sender])\n        \n        max_sender = None\n        for sender in senders:\n            if count_by_sender[sender] == max_messages and (not max_sender or sender > max_sender):\n                max_sender = sender\n        \n        return max_sender\n```
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