leetcode-problemset/leetcode/problem/check-if-binary-string-has-at-most-one-segment-of-ones.html

<p>Given a binary string <code>s</code> <strong>​​​​​without leading zeros</strong>, return <code>true</code>​​​ <em>if </em><code>s</code><em> contains <strong>at most one contiguous segment of ones</strong></em>. Otherwise, return <code>false</code>.</p>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;1001&quot;
<strong>Output:</strong> false
<strong>Explanation: </strong>The ones do not form a contiguous segment.
</pre>

<p><strong>Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;110&quot;
<strong>Output:</strong> true</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 100</code></li>
	<li><code>s[i]</code>​​​​ is either <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
	<li><code>s[0]</code> is&nbsp;<code>&#39;1&#39;</code>.</li>
</ul>