Are you struggling with the “Rearrange Array Elements by Sign” problem on LeetCode? Don\u2019t worry! In this blog, we\u2019ll break down the problem, show you two ways to solve it (Brute Force and Optimal), and explain everything in simple, easy-to-understand English. Let\u2019s dive in!<\/p>\n\n\n\n
Here’s the [Problem Link<\/span><\/mark><\/a><\/strong>] to begin with.<\/p>\n\n\n You are given an array of integers. Your task is to rearrange the elements so that positive and negative numbers appear one after another, starting with a positive number. The number of positive and negative numbers will always be the same.<\/p>\n\n\n\n Input:<\/strong> Output:<\/strong> Explanation:<\/strong><\/p>\n\n\n\n Input:<\/strong> Output:<\/strong> Let\u2019s think about how we can solve this problem step by step, using the simplest method:<\/p>\n\n\n\n This approach is straightforward and easy to understand, even though it uses extra space for the two lists.<\/p>\n\n\n\nWhat Does the Problem Say?<\/h2>\n\n\n\n
Example 1<\/h3>\n\n\n\n
nums = [3, 1, -2, -5, 2, -4]<\/code><\/p>\n\n\n\n[3, -2, 1, -5, 2, -4]<\/code><\/p>\n\n\n\n\n
3<\/code>), the second is negative (-2<\/code>), the third is positive (1<\/code>), the fourth is negative (-5<\/code>), and so on.<\/li>\n<\/ul>\n\n\n\nExample 2<\/h3>\n\n\n\n
nums = [-1, 1]<\/code><\/p>\n\n\n\n[1, -1]<\/code><\/p>\n\n\n\nBrute Force Solution<\/h2>\n\n\n\n
Intuition and Approach<\/h3>\n\n\n\n
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First, we need to separate the positive numbers and the negative numbers into two different lists. This way, we know exactly where all the positives and all the negatives are.<\/li>\n\n\n\n
Next, we want to place the numbers back into the original array in an alternating order: first a positive, then a negative, then a positive, and so on.<\/li>\n\n\n\n
Since the number of positive and negative numbers is always the same, we won\u2019t run out of either type while rearranging. By first collecting all positives and negatives, and then placing them back one by one, we make sure the order is correct.<\/li>\n<\/ol>\n\n\n\nCode Implementation<\/h3>\n\n\n\n