1304 .Find N Unique Integers Sum up to Zero LeetCode

 Given an integer n, return any array containing n unique integers such that they add up to 0.

Example 1:


Input: n = 5

Output: [-7,-1,1,3,4]

Explanation: These arrays also are accepted [-5,-1,1,2,3] , [-3,-1,2,-2,4].

Example 2:


Input: n = 3

Output: [-1,0,1]

Example 3:


Input: n = 1

Output: [0]


🧠 Logic Summary:

  • Use pairs like (1, -1), (2, -2) to balance the sum to 0.

  • For even n, just these pairs are enough.

  • For odd n, you need an extra 0 in the center to make it up to n elements.

Input: n = 5
Output: [-2, -1, 0, 1, 2]   // sum = 0


class Solution {
    public int[] sumZero(int n) {

        int num = 1; // Start from 1
        int[] result = new int[n]; // Result array of size n

        //  Fill pairs like (1, -1), (2, -2), ...
        for (int i = 0; i < n / 2; i++) {
            result[i] = num;              // Positive number
            result[n - 1 - i] = -num;     // Negative counterpart
            num++;                        // Move to next number
        }

        //  If n is odd, put a 0 in the middle (0 balances itself)
        if (n % 2 != 0) {
            result[n / 2] = 0;
        }

        // Return the array where the sum of all elements is zero
        return result;
    }
}

 

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