leetcode-1304-easy

Find N Unique Integers Sum up to Zero

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]
Constraints:

1 <= n <= 1000

思路一： 两个数字一正一反，相加和就是0，例如 1 和 -1，2 和 -2. 对参数 n 完全分类，只可能出现以下两种情况

• n 偶数
• n 奇数

对于偶数，只要增加对应配对的数字即可，对于奇数，只需要在偶数上面再加上 0 即可

public int[] sumZero(int n) {
    int[] result = new int[n];
    int mid = n >> 1;

    int idx = 1;
    int j = 0;
    for (int i = 0; i < mid; i++) {
        result[j++] = idx;
        result[j++] = -(idx++);
    }

    if (n % 2 != 0) {
        result[n - 1] = 0;
    }

    return result;
}