Accounts Merge

class Solution:
    def accountsMerge(self, accounts: List[List[str]]) -> List[List[str]]:
        N = len(accounts)
        uf = [i for i in range(N)]

        def find(x: int) -> int:
            while x != uf[x]:
                uf[x] = uf[uf[x]]
                x = uf[x]
            return x

        def merge(u: int, v: int) -> bool:
            u, v = find(u), find(v)
            if u == v:
                return False
            uf[u] = v
            return True

        owner = {}
        for idx, account in enumerate(accounts):
            for email in account[1:]:
                if email in owner:
                    merge(idx, owner[email])
                else:
                    owner[email] = idx

        groups = defaultdict(list)
        for email, x in owner.items():
            groups[find(x)].append(email)

        return [
            [accounts[i][0]] + sorted(emails)
            for i, emails in groups.items()
        ]