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leetcode/problem/separate-black-and-white-balls.html

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+<p>There are <code>n</code> balls on a table, each ball has a color black or white.</p>
+
+<p>You are given a <strong>0-indexed</strong> binary string <code>s</code> of length <code>n</code>, where <code>1</code> and <code>0</code> represent black and white balls, respectively.</p>
+
+<p>In each step, you can choose two adjacent balls and swap them.</p>
+
+<p>Return <em>the <strong>minimum</strong> number of steps to group all the black balls to the right and all the white balls to the left</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;101&quot;
+<strong>Output:</strong> 1
+<strong>Explanation:</strong> We can group all the black balls to the right in the following way:
+- Swap s[0] and s[1], s = &quot;011&quot;.
+Initially, 1s are not grouped together, requiring at least 1 step to group them to the right.</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;100&quot;
+<strong>Output:</strong> 2
+<strong>Explanation:</strong> We can group all the black balls to the right in the following way:
+- Swap s[0] and s[1], s = &quot;010&quot;.
+- Swap s[1] and s[2], s = &quot;001&quot;.
+It can be proven that the minimum number of steps needed is 2.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;0111&quot;
+<strong>Output:</strong> 0
+<strong>Explanation:</strong> All the black balls are already grouped to the right.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= n == s.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>s[i]</code> is either <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
+</ul>