<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:
    def invalidTransactions(self, transactions: List[str]) -> List[str]:
#have a hashmap to map name with idx. iterate through transactions, if amount > 1000, to res set add idx. else go through transactions and check if time diff <= 60 and cities are same or not.      
        hmap = {}
        res = set()

        for i, t in enumerate(transactions): #iterate through list, if name not in map, 
            name, time, amount, city = t.split(",") #create empty list for the name. if 
            if name not in hmap: #amt > 1k, add idx to res. if name already in map, get
                hmap[name] = [] #the indices and store in prev
                if int(amount) > 1000:
                    res.add(i)
            else:
                prev = hmap[name] #iterate through len of prev indices and get all trans
                for j in range(len(prev)): #details of that idx in prev
                    prev_name, prev_time, prev_amt, prev_city = transactions[prev[j]].split(",")
                    if int(amount) > 1000: #same check again, amt > 1k, add idx to res
                        res.add(i) #if time diff <= 60 and diff city, add i and prev idx
                    if abs(int(time) - int(prev_time)) <= 60 and city != prev_city: #to res
                        res.add(i)
                        res.add(prev[j])
            hmap[name].append(i) #if name not in map, add its idx to map. 
        
        return [transactions[t] for t in res] #for every idx in res, get the transaction
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