LeetCode 2149: Rearrange Array Elements by Sign Solution

Master LeetCode problem 2149 (Rearrange Array Elements by Sign), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2149. Rearrange Array Elements by Sign

Medium

Array Two Pointers Simulation

Problem Explanation

Explanation

To rearrange the array elements by sign, we can follow these steps:

Separate the positive and negative integers into two separate lists.
Sort both lists in descending order of absolute values.
Merge the two lists alternately starting with a positive integer.

Time Complexity: O(nlogn) where n is the length of the input array nums. Space Complexity: O(n) where n is the length of the input array nums.

Solution Code

import java.util.*;

class Solution {
    public int[] rearrangeArrayBySign(int[] nums) {
        List<Integer> positive = new ArrayList<>();
        List<Integer> negative = new ArrayList<>();
        
        for (int num : nums) {
            if (num > 0) {
                positive.add(num);
            } else {
                negative.add(num);
            }
        }
        
        Collections.sort(positive, Collections.reverseOrder());
        Collections.sort(negative, Collections.reverseOrder());
        
        int[] result = new int[nums.length];
        int i = 0, j = 0;
        
        for (int k = 0; k < nums.length; k++) {
            if (k % 2 == 0) {
                result[k] = positive.get(i++);
            } else {
                result[k] = negative.get(j++);
            }
        }
        
        return result;
    }
}

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