14-Rearrange-Array-Elements-by-Sign.md

Rearrange Array Elements by Sign

Problem Link

https://leetcode.com/problems/rearrange-array-elements-by-sign/

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Pattern

• Two Pointer
• In-place

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Approach

Use two pointers to place positive and negative elements alternately or collect and rebuild.

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Time Complexity

O(n)

Space Complexity

O(1) or O(n) depending on method

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Java Solution (one approach)

class Solution {
    public int[] rearrangeArray(int[] nums) {
        int[] res = new int[nums.length];
        int pos = 0, neg = 1;
        for (int n : nums) {
            if (n > 0) { res[pos] = n; pos += 2; }
            else { res[neg] = n; neg += 2; }
        }
        return res;
    }
}