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leetcode/problem/rearrange-array-elements-by-sign.html

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+<p>You are given a <strong>0-indexed</strong> integer array <code>nums</code> of <strong>even</strong> length consisting of an <strong>equal</strong> number of positive and negative integers.</p>
+
+<p>You should <strong>rearrange</strong> the elements of <code>nums</code> such that the modified array follows the given conditions:</p>
+
+<ol>
+	<li>Every <strong>consecutive pair</strong> of integers have <strong>opposite signs</strong>.</li>
+	<li>For all integers with the same sign, the <strong>order</strong> in which they were present in <code>nums</code> is <strong>preserved</strong>.</li>
+	<li>The rearranged array begins with a positive integer.</li>
+</ol>
+
+<p>Return <em>the modified array after rearranging the elements to satisfy the aforementioned conditions</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [3,1,-2,-5,2,-4]
+<strong>Output:</strong> [3,-2,1,-5,2,-4]
+<strong>Explanation:</strong>
+The positive integers in nums are [3,1,2]. The negative integers are [-2,-5,-4].
+The only possible way to rearrange them such that they satisfy all conditions is [3,-2,1,-5,2,-4].
+Other ways such as [1,-2,2,-5,3,-4], [3,1,2,-2,-5,-4], [-2,3,-5,1,-4,2] are incorrect because they do not satisfy one or more conditions.  
+</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [-1,1]
+<strong>Output:</strong> [1,-1]
+<strong>Explanation:</strong>
+1 is the only positive integer and -1 the only negative integer in nums.
+So nums is rearranged to [1,-1].
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>2 &lt;= nums.length &lt;= 2 * 10<sup>5</sup></code></li>
+	<li><code>nums.length</code> is <strong>even</strong></li>
+	<li><code>1 &lt;= |nums[i]| &lt;= 10<sup>5</sup></code></li>
+	<li><code>nums</code> consists of <strong>equal</strong> number of positive and negative integers.</li>
+</ul>