Minimum Number of Operations to Convert Time
<p>You are given two strings <code>current</code> and <code>correct</code> representing two <strong>24-hour times</strong>.</p>

<p>24-hour times are formatted as <code>&quot;HH:MM&quot;</code>, where <code>HH</code> is between <code>00</code> and <code>23</code>, and <code>MM</code> is between <code>00</code> and <code>59</code>. The earliest 24-hour time is <code>00:00</code>, and the latest is <code>23:59</code>.</p>

<p>In one operation you can increase the time <code>current</code> by <code>1</code>, <code>5</code>, <code>15</code>, or <code>60</code> minutes. You can perform this operation <strong>any</strong> number of times.</p>

<p>Return <em>the <strong>minimum number of operations</strong> needed to convert </em><code>current</code><em> to </em><code>correct</code>.</p>

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

<pre>
<strong>Input:</strong> current = &quot;02:30&quot;, correct = &quot;04:35&quot;
<strong>Output:</strong> 3
<strong>Explanation:
</strong>We can convert current to correct in 3 operations as follows:
- Add 60 minutes to current. current becomes &quot;03:30&quot;.
- Add 60 minutes to current. current becomes &quot;04:30&quot;.
- Add 5 minutes to current. current becomes &quot;04:35&quot;.
It can be proven that it is not possible to convert current to correct in fewer than 3 operations.</pre>

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

<pre>
<strong>Input:</strong> current = &quot;11:00&quot;, correct = &quot;11:01&quot;
<strong>Output:</strong> 1
<strong>Explanation:</strong> We only have to add one minute to current, so the minimum number of operations needed is 1.
</pre>

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

<ul>
	<li><code>current</code> and <code>correct</code> are in the format <code>&quot;HH:MM&quot;</code></li>
	<li><code>current &lt;= correct</code></li>
</ul>
Greedy; String
class Solution:
    def convertTime(self, current: str, correct: str) -> int:
        a = int(current[:2]) * 60 + int(current[3:])
        b = int(correct[:2]) * 60 + int(correct[3:])
        ans, d = 0, b - a
        for i in [60, 15, 5, 1]:
            ans += d // i
            d %= i
        return ans
