Sync LeetCode submission Runtime - 48 ms (37.79%), Memory - 19.7 MB (13.90%)

Author: jimit105

1371-minimum-remove-to-make-valid-parentheses/README.md

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+<p>Given a string <font face="monospace">s</font> of <code>&#39;(&#39;</code> , <code>&#39;)&#39;</code> and lowercase English characters.</p>
+
+<p>Your task is to remove the minimum number of parentheses ( <code>&#39;(&#39;</code> or <code>&#39;)&#39;</code>, in any positions ) so that the resulting <em>parentheses string</em> is valid and return <strong>any</strong> valid string.</p>
+
+<p>Formally, a <em>parentheses string</em> is valid if and only if:</p>
+
+<ul>
+	<li>It is the empty string, contains only lowercase characters, or</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>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;lee(t(c)o)de)&quot;
+<strong>Output:</strong> &quot;lee(t(c)o)de&quot;
+<strong>Explanation:</strong> &quot;lee(t(co)de)&quot; , &quot;lee(t(c)ode)&quot; would also be accepted.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;a)b(c)d&quot;
+<strong>Output:</strong> &quot;ab(c)d&quot;
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;))((&quot;
+<strong>Output:</strong> &quot;&quot;
+<strong>Explanation:</strong> An empty string is also valid.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>s[i]</code> is either&nbsp;<code>&#39;(&#39;</code> , <code>&#39;)&#39;</code>, or lowercase English letter.</li>
+</ul>

1371-minimum-remove-to-make-valid-parentheses/solution.py

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+# Approach 1: Using Stack and String Builder
+
+# Time: O(n)
+# Space: O(n)
+
+class Solution:
+    def minRemoveToMakeValid(self, s: str) -> str:
+        indices_to_remove = set()
+        stack = [] # tracks the index
+
+        for i, c in enumerate(s):
+            if c not in "()":
+                continue
+            elif c == '(':
+                stack.append(i)
+            elif not stack:
+                indices_to_remove.add(i)
+            elif c == ')':
+                stack.pop()
+
+        indices_to_remove = indices_to_remove.union(set(stack))
+
+        string_builder = []
+        for i, c in enumerate(s):
+            if i not in indices_to_remove:
+                string_builder.append(c)
+
+        return ''.join(string_builder)
+