Minimum Length of String After Operations
<p>You are given a string <code>s</code>.</p>

<p>You can perform the following process on <code>s</code> <strong>any</strong> number of times:</p>

<ul>
	<li>Choose an index <code>i</code> in the string such that there is <strong>at least</strong> one character to the left of index <code>i</code> that is equal to <code>s[i]</code>, and <strong>at least</strong> one character to the right that is also equal to <code>s[i]</code>.</li>
	<li>Delete the <strong>closest</strong> occurrence of <code>s[i]</code> located to the <strong>left</strong> of <code>i</code>.</li>
	<li>Delete the <strong>closest</strong> occurrence of <code>s[i]</code> located to the <strong>right</strong> of <code>i</code>.</li>
</ul>

<p>Return the <strong>minimum</strong> length of the final string <code>s</code> that you can achieve.</p>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;abaacbcbb&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">5</span></p>

<p><strong>Explanation:</strong><br />
We do the following operations:</p>

<ul>
	<li>Choose index 2, then remove the characters at indices 0 and 3. The resulting string is <code>s = &quot;bacbcbb&quot;</code>.</li>
	<li>Choose index 3, then remove the characters at indices 0 and 5. The resulting string is <code>s = &quot;acbcb&quot;</code>.</li>
</ul>
</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;aa&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">2</span></p>

<p><strong>Explanation:</strong><br />
We cannot perform any operations, so we return the length of the original string.</p>
</div>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 2 * 10<sup>5</sup></code></li>
	<li><code>s</code> consists only of lowercase English letters.</li>
</ul>
Hash Table; String; Counting
class Solution {
    public int minimumLength(String s) {
        int[] cnt = new int[26];
        for (int i = 0; i < s.length(); ++i) {
            ++cnt[s.charAt(i) - 'a'];
        }
        int ans = 0;
        for (int x : cnt) {
            if (x > 0) {
                ans += x % 2 == 1 ? 1 : 2;
            }
        }
        return ans;
    }
}