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0957-minimum-add-to-make-parentheses-valid/README.md

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+<p>A parentheses string is valid if and only if:</p>
+
+<ul>
+	<li>It is the empty string,</li>
+	<li>It can be written as <code>AB</code> (<code>A</code> concatenated with <code>B</code>), where <code>A</code> and <code>B</code> are valid strings, or</li>
+	<li>It can be written as <code>(A)</code>, where <code>A</code> is a valid string.</li>
+</ul>
+
+<p>You are given a parentheses string <code>s</code>. In one move, you can insert a parenthesis at any position of the string.</p>
+
+<ul>
+	<li>For example, if <code>s = &quot;()))&quot;</code>, you can insert an opening parenthesis to be <code>&quot;(<strong>(</strong>)))&quot;</code> or a closing parenthesis to be <code>&quot;())<strong>)</strong>)&quot;</code>.</li>
+</ul>
+
+<p>Return <em>the minimum number of moves required to make </em><code>s</code><em> valid</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;())&quot;
+<strong>Output:</strong> 1
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;(((&quot;
+<strong>Output:</strong> 3
+</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;(&#39;</code> or <code>&#39;)&#39;</code>.</li>
+</ul>

0957-minimum-add-to-make-parentheses-valid/solution.py

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+# Approach: Open Bracket Counter
+
+# Time: O(n)
+# Space: O(1)
+
+class Solution:
+    def minAddToMakeValid(self, s: str) -> int:
+        open_brackets = 0
+        min_adds_required = 0
+
+        for c in s:
+            if c == '(':
+                open_brackets += 1
+            else:
+                if open_brackets > 0:
+                    open_brackets -= 1
+                else:
+                    min_adds_required += 1
+
+        return min_adds_required + open_brackets