<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>

class Solution:
    def minSwaps(self, s):
        c_one, c_zero = s.count("1"), s.count("0")

        if abs(c_one-c_zero) > 1:
            return -1 

        def function(t,val):
            n, total = len(t), 0

            for i in range(n):
                if val != int(t[i]):
                    total += 1 
                val = val^1

            return total//2 

        if c_one > c_zero:
            return function(s,1)

        if c_zero > c_one:
            return function(s,0)

        if c_zero == c_one:
            return min(function(s,0),function(s,1))
16700