<p>You are given the string <code>croakOfFrogs</code>, which represents a combination of the string <code>&quot;croak&quot;</code> from different frogs, that is, multiple frogs can croak at the same time, so multiple <code>&quot;croak&quot;</code> are mixed.</p>

<p><em>Return the minimum number of </em>different<em> frogs to finish all the croaks in the given string.</em></p>

<p>A valid <code>&quot;croak&quot;</code> means a frog is printing five letters <code>&#39;c&#39;</code>, <code>&#39;r&#39;</code>, <code>&#39;o&#39;</code>, <code>&#39;a&#39;</code>, and <code>&#39;k&#39;</code> <strong>sequentially</strong>. The frogs have to print all five letters to finish a croak. If the given string is not a combination of a valid <code>&quot;croak&quot;</code> return <code>-1</code>.</p>

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

<pre>
<strong>Input:</strong> croakOfFrogs = &quot;croakcroak&quot;
<strong>Output:</strong> 1 
<strong>Explanation:</strong> One frog yelling &quot;croak<strong>&quot;</strong> twice.
</pre>

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

<pre>
<strong>Input:</strong> croakOfFrogs = &quot;crcoakroak&quot;
<strong>Output:</strong> 2 
<strong>Explanation:</strong> The minimum number of frogs is two. 
The first frog could yell &quot;<strong>cr</strong>c<strong>oak</strong>roak&quot;.
The second frog could yell later &quot;cr<strong>c</strong>oak<strong>roak</strong>&quot;.
</pre>

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

<pre>
<strong>Input:</strong> croakOfFrogs = &quot;croakcrook&quot;
<strong>Output:</strong> -1
<strong>Explanation:</strong> The given string is an invalid combination of &quot;croak<strong>&quot;</strong> from different frogs.
</pre>

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

<ul>
	<li><code>1 &lt;= croakOfFrogs.length &lt;= 10<sup>5</sup></code></li>
	<li><code>croakOfFrogs</code> is either <code>&#39;c&#39;</code>, <code>&#39;r&#39;</code>, <code>&#39;o&#39;</code>, <code>&#39;a&#39;</code>, or <code>&#39;k&#39;</code>.</li>
</ul>

#pragma GCC optimize("O3")
int _ = [](){ios_base::sync_with_stdio(false);cin.tie(nullptr);return 0;}();

class Solution
{
public:
    int minNumberOfFrogs(const string& croakOfFrogs) const
    {
        int maxCroaking = 0;
        int currentCroaking = 0;
        int stageC = 0;
        int stageR = 0;
        int stageO = 0;
        int stageA = 0;

        for (const char c : croakOfFrogs)
        {
            switch (c)
            {
            case 'c':
                ++stageC;
                ++currentCroaking;
                maxCroaking = max(maxCroaking, currentCroaking);
                break;
            case 'r':
                if (stageC == 0)
                    return -1;

                --stageC;
                ++stageR;
                break;
            case 'o':
                if (stageR == 0)
                    return -1;

                --stageR;
                ++stageO;
                break;
            case 'a':
                if (stageO == 0)
                    return -1;

                --stageO;
                ++stageA;
                break;
            case 'k':
                if (stageA == 0)
                    return -1;

                --stageA;
                --currentCroaking;
                break;
            }
        }

        if (currentCroaking != 0)
            return -1;

        return maxCroaking;
    }
};
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