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leetcode/problem/validate-stack-sequences.html

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+<p>Given two integer arrays <code>pushed</code> and <code>popped</code> each with distinct values, return <code>true</code><em> if this could have been the result of a sequence of push and pop operations on an initially empty stack, or </em><code>false</code><em> otherwise.</em></p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> pushed = [1,2,3,4,5], popped = [4,5,3,2,1]
+<strong>Output:</strong> true
+<strong>Explanation:</strong> We might do the following sequence:
+push(1), push(2), push(3), push(4),
+pop() -&gt; 4,
+push(5),
+pop() -&gt; 5, pop() -&gt; 3, pop() -&gt; 2, pop() -&gt; 1
+</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> pushed = [1,2,3,4,5], popped = [4,3,5,1,2]
+<strong>Output:</strong> false
+<strong>Explanation:</strong> 1 cannot be popped before 2.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= pushed.length &lt;= 1000</code></li>
+	<li><code>0 &lt;= pushed[i] &lt;= 1000</code></li>
+	<li>All the elements of <code>pushed</code> are <strong>unique</strong>.</li>
+	<li><code>popped.length == pushed.length</code></li>
+	<li><code>popped</code> is a permutation of <code>pushed</code>.</li>
+</ul>