Rearrange Array Elements by Sign — LeetCode 2149 Python Solution

The problem

You are given a 0-indexed integer array nums of even length consisting of an equal number of positive and negative integers. You should return the array of nums such that the array follows the given conditions: Every consecutive pair of integers have opposite signs.

Example

Input

nums = [3,1,-2,-5,2,-4]

Output

[3,-2,1,-5,2,-4]

Explanation

The positive integers in nums are [3,1,2]. The negative integers are [-2,-5,-4].

Python solution

class Solution:
    def rearrangeArray(self, nums: List[int]) -> List[int]:
        ans = [0] * len(nums)
        i, j = 0, 1
        for x in nums:
            if x > 0:
                ans[i] = x
                i += 2
            else:
                ans[j] = x
                j += 2
        return ans

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 2149. Rearrange Array Elements by Sign is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Two Pointers.

The two pointers guide has the Python template for the pattern and the 201 LeetCode problems that use it.

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