Calculate Amount Paid in Taxes
<p>You are given a <strong>0-indexed</strong> 2D integer array <code>brackets</code> where <code>brackets[i] = [upper<sub>i</sub>, percent<sub>i</sub>]</code> means that the <code>i<sup>th</sup></code> tax bracket has an upper bound of <code>upper<sub>i</sub></code> and is taxed at a rate of <code>percent<sub>i</sub></code>. The brackets are <strong>sorted</strong> by upper bound (i.e. <code>upper<sub>i-1</sub> &lt; upper<sub>i</sub></code> for <code>0 &lt; i &lt; brackets.length</code>).</p>

<p>Tax is calculated as follows:</p>

<ul>
	<li>The first <code>upper<sub>0</sub></code> dollars earned are taxed at a rate of <code>percent<sub>0</sub></code>.</li>
	<li>The next <code>upper<sub>1</sub> - upper<sub>0</sub></code> dollars earned are taxed at a rate of <code>percent<sub>1</sub></code>.</li>
	<li>The next <code>upper<sub>2</sub> - upper<sub>1</sub></code> dollars earned are taxed at a rate of <code>percent<sub>2</sub></code>.</li>
	<li>And so on.</li>
</ul>

<p>You are given an integer <code>income</code> representing the amount of money you earned. Return <em>the amount of money that you have to pay in taxes.</em> Answers within <code>10<sup>-5</sup></code> of the actual answer will be accepted.</p>

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

<pre>
<strong>Input:</strong> brackets = [[3,50],[7,10],[12,25]], income = 10
<strong>Output:</strong> 2.65000
<strong>Explanation:</strong>
Based on your income, you have 3 dollars in the 1<sup>st</sup> tax bracket, 4 dollars in the 2<sup>nd</sup> tax bracket, and 3 dollars in the 3<sup>rd</sup> tax bracket.
The tax rate for the three tax brackets is 50%, 10%, and 25%, respectively.
In total, you pay $3 * 50% + $4 * 10% + $3 * 25% = $2.65 in taxes.
</pre>

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

<pre>
<strong>Input:</strong> brackets = [[1,0],[4,25],[5,50]], income = 2
<strong>Output:</strong> 0.25000
<strong>Explanation:</strong>
Based on your income, you have 1 dollar in the 1<sup>st</sup> tax bracket and 1 dollar in the 2<sup>nd</sup> tax bracket.
The tax rate for the two tax brackets is 0% and 25%, respectively.
In total, you pay $1 * 0% + $1 * 25% = $0.25 in taxes.
</pre>

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

<pre>
<strong>Input:</strong> brackets = [[2,50]], income = 0
<strong>Output:</strong> 0.00000
<strong>Explanation:</strong>
You have no income to tax, so you have to pay a total of $0 in taxes.
</pre>

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

<ul>
	<li><code>1 &lt;= brackets.length &lt;= 100</code></li>
	<li><code>1 &lt;= upper<sub>i</sub> &lt;= 1000</code></li>
	<li><code>0 &lt;= percent<sub>i</sub> &lt;= 100</code></li>
	<li><code>0 &lt;= income &lt;= 1000</code></li>
	<li><code>upper<sub>i</sub></code> is sorted in ascending order.</li>
	<li>All the values of <code>upper<sub>i</sub></code> are <strong>unique</strong>.</li>
	<li>The upper bound of the last tax bracket is greater than or equal to <code>income</code>.</li>
</ul>
Array; Simulation
func calculateTax(brackets [][]int, income int) float64 {
	var ans, prev int
	for _, e := range brackets {
		upper, percent := e[0], e[1]
		ans += max(0, min(income, upper)-prev) * percent
		prev = upper
	}
	return float64(ans) / 100.0
}