Merge accounts with the same email address.

mergeAccounts.swift

class Solution {
    func accountsMerge(_ accounts: [[String]]) -> [[String]] {
        var accounts: [Account] = accounts.map {
            var account = Account(name: $0.first!)
            for i in 1 ..< $0.count {
                account.emails.insert($0[i])
            }
            return account
        }
        
        var i = 0
        while i < accounts.count {
            for j in i + 1 ..< accounts.count {
                let hasDuplicateEmail = !accounts[i].emails.isDisjoint(with: accounts[j].emails)
                if !hasDuplicateEmail { continue }
                accounts[i].emails.formUnion(accounts[j].emails)
                accounts.remove(at: j)
                i -= 1
                break
            }
            i += 1
        }
        
        return accounts.map {
            var account: [String] = []
            account.append($0.name)
            for email in $0.emails.sorted() {
                account.append(email)
            }
            return account
        }
    }
    
    struct Account {
        var name: String
        var emails: Set<String> = []
    }
            
}