Invalid Transactions
<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>
Array; Hash Table; String; Sorting
class Solution {
    public List<String> invalidTransactions(String[] transactions) {
        Map<String, List<Item>> d = new HashMap<>();
        Set<Integer> idx = new HashSet<>();
        for (int i = 0; i < transactions.length; ++i) {
            var e = transactions[i].split(",");
            String name = e[0];
            int time = Integer.parseInt(e[1]);
            int amount = Integer.parseInt(e[2]);
            String city = e[3];
            d.computeIfAbsent(name, k -> new ArrayList<>()).add(new Item(time, city, i));
            if (amount > 1000) {
                idx.add(i);
            }
            for (Item item : d.get(name)) {
                if (!city.equals(item.city) && Math.abs(time - item.t) <= 60) {
                    idx.add(i);
                    idx.add(item.i);
                }
            }
        }
        List<String> ans = new ArrayList<>();
        for (int i : idx) {
            ans.add(transactions[i]);
        }
        return ans;
    }
}

class Item {
    int t;
    String city;
    int i;

    Item(int t, String city, int i) {
        this.t = t;
        this.city = city;
        this.i = i;
    }
}