Leetcode 973. K Closest Points to Origin

Given an array of points where points[i] = [xi, yi] represents a point on the X-Y plane and an integer k, return the k closest points to the origin (0, 0).

The distance between two points on the X-Y plane is the Euclidean distance (i.e., √(x1 - x2)2 + (y1 - y2)2).

You may return the answer in any order. The answer is guaranteed to be unique (except for the order that it is in).

Example 1:

Input: points = [[1,3],[-2,2]], k = 1

Output: [[-2,2]]

Explanation:The distance between (1, 3) and the origin is sqrt(10). The distance between (-2, 2) and the origin is sqrt(8). Since sqrt(8) < sqrt(10), (-2, 2) is closer to the origin. We only want the closest k = 1 points from the origin, so the answer is just [[-2,2]].

Example 2:

Input: points = [[3,3],[5,-1],[-2,4]], k = 2

Output: [[3,3],[-2,4]]

Explanation: The answer [[-2,4],[3,3]] would also be accepted.

Constraints:

• 1 <= k <= points.length <= 104

• -104 < xi, yi < 104

中等难度，返回距离0最近的k个点，不论顺序，就是求每个点的长度，然后把index保存住，排序，然后把前k个放到数组里面， 返回即可；

因为是平方，所以担心的是int类型溢出的问题，所以使用了long的数组保存距离了。

Runtime: 36 ms, faster than 63.44% of Java online submissions for K Closest Points to Origin.

Memory Usage: 50.9 MB, less than 36.51% of Java online submissions for K Closest Points to Origin.