<p>A transaction is possibly invalid if:</p>

<ul>
	<li>the amount exceeds <code>$1000</code>, or;</li>
	<li>if it occurs within (and including) <code>60</code> minutes of another transaction with the <strong>same name</strong> in a <strong>different city</strong>.</li>
</ul>

<p>You are given an array of strings <code>transaction</code> where <code>transactions[i]</code> consists of comma-separated values representing the name, time (in minutes), amount, and city of the transaction.</p>

<p>Return a list of <code>transactions</code> that are possibly invalid. You may return the answer in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> transactions = [&quot;alice,20,800,mtv&quot;,&quot;alice,50,100,beijing&quot;]
<strong>Output:</strong> [&quot;alice,20,800,mtv&quot;,&quot;alice,50,100,beijing&quot;]
<strong>Explanation:</strong> The first transaction is invalid because the second transaction occurs within a difference of 60 minutes, have the same name and is in a different city. Similarly the second one is invalid too.</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> transactions = [&quot;alice,20,800,mtv&quot;,&quot;alice,50,1200,mtv&quot;]
<strong>Output:</strong> [&quot;alice,50,1200,mtv&quot;]
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> transactions = [&quot;alice,20,800,mtv&quot;,&quot;bob,50,1200,mtv&quot;]
<strong>Output:</strong> [&quot;bob,50,1200,mtv&quot;]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>transactions.length &lt;= 1000</code></li>
	<li>Each <code>transactions[i]</code> takes the form <code>&quot;{name},{time},{amount},{city}&quot;</code></li>
	<li>Each <code>{name}</code> and <code>{city}</code> consist of lowercase English letters, and have lengths between <code>1</code> and <code>10</code>.</li>
	<li>Each <code>{time}</code> consist of digits, and represent an integer between <code>0</code> and <code>1000</code>.</li>
	<li>Each <code>{amount}</code> consist of digits, and represent an integer between <code>0</code> and <code>2000</code>.</li>
</ul>

class Solution {
    struct Transaction{
        string name;
        int min;
        int amount;
        string city;
        
        bool operator <(const Transaction& t2) const{
            return name < t2.name || (name == t2.name && min < t2.min);
        }
        string toString() const{
            std::stringstream ss;
            ss << name << kDelimiter << min << kDelimiter << amount << kDelimiter << city;
            return ss.str();
        }
    };
    static constexpr char kDelimiter = ',';
    vector<Transaction> parseTransactions(const vector<string>& transactions){
        vector<Transaction> output;
        for(auto& transaction : transactions){
            string name, min_s, amount_s, city;
            stringstream ss(transaction);
            getline(ss, name, kDelimiter);
            getline(ss, min_s, kDelimiter);
            getline(ss, amount_s, kDelimiter);
            getline(ss, city, kDelimiter);
            
            output.emplace_back(name, stoi(min_s), stoi(amount_s), city);
        }
        return output;
    }
public:
    vector<string> invalidTransactions(vector<string>& transactions) {
        // Parse transactions
        vector<Transaction> ts = parseTransactions(transactions);
        // Order transactions
        sort(ts.begin(), ts.end());
        vector<string> res;
        const int n_transactions = ts.size();
        vector<bool> invalid(n_transactions, false);
        
        for(int i = 0; i < n_transactions; i++){
            auto& transaction = ts[i];
            
            //std::cout << transaction.toString() << std::endl;
            if(transaction.amount > 1000){
                //std::cout << "Over amount " << std::endl;
                if(!invalid[i]){
                    res.push_back(transaction.toString());
                }
                invalid[i] = true;
            }
            // Check if it is within 60 min of any other transaction with the same name and different city
            const int time_limit = transaction.min + 60;
            for(int j = i+1; j < n_transactions; j++){
                auto& other_transaction = ts[j];
                //std::cout << "Checking against " << other_transaction.toString() << std::endl;
                if(other_transaction.min <= time_limit){
                    if(other_transaction.name == transaction.name && other_transaction.city != transaction.city){
                        //std::cout << "INVALID" << std::endl;
                        if(!invalid[i]){
                            res.push_back(transaction.toString());
                        }
                        if(!invalid[j]){
                            res.push_back(other_transaction.toString());
                        }
                        invalid[i] = true;
                        invalid[j] = true;
                    }
                }else{
                    break;
                }

            }
        }
        return res;
    }
};
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