Maximum Score From Removing Substrings
<p>You are given a string <code>s</code> and two integers <code>x</code> and <code>y</code>. You can perform two types of operations any number of times.</p>

<ul>
	<li>Remove substring <code>&quot;ab&quot;</code> and gain <code>x</code> points.

    <ul>
    	<li>For example, when removing <code>&quot;ab&quot;</code> from <code>&quot;c<u>ab</u>xbae&quot;</code> it becomes <code>&quot;cxbae&quot;</code>.</li>
    </ul>
    </li>
    <li>Remove substring <code>&quot;ba&quot;</code> and gain <code>y</code> points.
    <ul>
    	<li>For example, when removing <code>&quot;ba&quot;</code> from <code>&quot;cabx<u>ba</u>e&quot;</code> it becomes <code>&quot;cabxe&quot;</code>.</li>
    </ul>
    </li>

</ul>

<p>Return <em>the maximum points you can gain after applying the above operations on</em> <code>s</code>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;cdbcbbaaabab&quot;, x = 4, y = 5
<strong>Output:</strong> 19
<strong>Explanation:</strong>
- Remove the &quot;ba&quot; underlined in &quot;cdbcbbaaa<u>ba</u>b&quot;. Now, s = &quot;cdbcbbaaab&quot; and 5 points are added to the score.
- Remove the &quot;ab&quot; underlined in &quot;cdbcbbaa<u>ab</u>&quot;. Now, s = &quot;cdbcbbaa&quot; and 4 points are added to the score.
- Remove the &quot;ba&quot; underlined in &quot;cdbcb<u>ba</u>a&quot;. Now, s = &quot;cdbcba&quot; and 5 points are added to the score.
- Remove the &quot;ba&quot; underlined in &quot;cdbc<u>ba</u>&quot;. Now, s = &quot;cdbc&quot; and 5 points are added to the score.
Total score = 5 + 4 + 5 + 5 = 19.</pre>

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

<pre>
<strong>Input:</strong> s = &quot;aabbaaxybbaabb&quot;, x = 5, y = 4
<strong>Output:</strong> 20
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= x, y &lt;= 10<sup>4</sup></code></li>
	<li><code>s</code> consists of lowercase English letters.</li>
</ul>
Stack; Greedy; String
impl Solution {
    pub fn maximum_gain(s: String, mut x: i32, mut y: i32) -> i32 {
        let (mut a, mut b) = ('a', 'b');
        if x < y {
            std::mem::swap(&mut x, &mut y);
            std::mem::swap(&mut a, &mut b);
        }

        let mut ans = 0;
        let mut cnt1 = 0;
        let mut cnt2 = 0;

        for c in s.chars() {
            if c == a {
                cnt1 += 1;
            } else if c == b {
                if cnt1 > 0 {
                    ans += x;
                    cnt1 -= 1;
                } else {
                    cnt2 += 1;
                }
            } else {
                ans += cnt1.min(cnt2) * y;
                cnt1 = 0;
                cnt2 = 0;
            }
        }

        ans += cnt1.min(cnt2) * y;
        ans
    }
}
