<p>Given a binary string <code>s</code>, return <em>the <strong>minimum</strong> number of character swaps to make it <strong>alternating</strong>, or </em><code>-1</code><em> if it is impossible.</em></p>

<p>The string is called <strong>alternating</strong> if no two adjacent characters are equal. For example, the strings <code>&quot;010&quot;</code> and <code>&quot;1010&quot;</code> are alternating, while the string <code>&quot;0100&quot;</code> is not.</p>

<p>Any two characters may be swapped, even if they are&nbsp;<strong>not adjacent</strong>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;111000&quot;
<strong>Output:</strong> 1
<strong>Explanation:</strong> Swap positions 1 and 4: &quot;1<u>1</u>10<u>0</u>0&quot; -&gt; &quot;1<u>0</u>10<u>1</u>0&quot;
The string is now alternating.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;010&quot;
<strong>Output:</strong> 0
<strong>Explanation:</strong> The string is already alternating, no swaps are needed.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;1110&quot;
<strong>Output:</strong> -1
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
	<li><code>s[i]</code> is either <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
</ul>

# 1 pass check count 0 and 1
# if even: if not ==, return -1 else : return min (start with0, start with 1)
# else: if

class Solution:
    def minSwaps(self, s: str) -> int:
        n = len(s)
        def helper(c):
            count = 0
            for i in range(0, n, 2):
                if s[i] != c:
                    count += 1
            return count
        count_0, count_1 = 0, 0
        for c in s:
            if c == '0':
                count_0 += 1
            else:
                count_1 += 1
        if n % 2 == 0:
            if count_0 == count_1:
                return min(helper('0'), helper('1'))
            else:
                return -1
        else:
            if count_0 - count_1 == 1:
                return helper('0')
            elif count_1 - count_0 == 1:
                return helper('1')
            else:
                return -1
16600