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0020-valid-parentheses/README.md

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+<h2><a href="https://leetcode.com/problems/valid-parentheses/">20. Valid Parentheses</a></h2><h3>Easy</h3><hr><div><p>Given a string <code>s</code> containing just the characters <code>'('</code>, <code>')'</code>, <code>'{'</code>, <code>'}'</code>, <code>'['</code> and <code>']'</code>, determine if the input string is valid.</p>
+
+<p>An input string is valid if:</p>
+
+<ol>
+	<li>Open brackets must be closed by the same type of brackets.</li>
+	<li>Open brackets must be closed in the correct order.</li>
+	<li>Every close bracket has a corresponding open bracket of the same type.</li>
+</ol>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre><strong>Input:</strong> s = "()"
+<strong>Output:</strong> true
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre><strong>Input:</strong> s = "()[]{}"
+<strong>Output:</strong> true
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre><strong>Input:</strong> s = "(]"
+<strong>Output:</strong> false
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= s.length &lt;= 10<sup>4</sup></code></li>
+	<li><code>s</code> consists of parentheses only <code>'()[]{}'</code>.</li>
+</ul>
+</div>