leetcode记录:难度简单：973. K Closest Points to Origin（离原点最近的K个坐标）

题目出处：https://leetcode.com/problems/k-closest-points-to-origin/

题目描述：

我们有一个平面上的点的列表。求离原点(0,0)最近的K个点。(这里，平面上两点之间的距离是欧几里得距离)你可以按任何顺序回答。答案是唯一的(除了它的顺序)。

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]]
(The answer [[-2,4],[3,3]] would also be accepted.)

思路：

计算points里面的单个坐标离原点的距离，从小到大排列，取前面的K个数值，返回对应的坐标。

有一点要注意，要是对计算后的距离排序，无法再对这个距离对应的坐标进行还原，所以只能用一个function包含起来

var kClosest = function(points, K) {
    function fn(A) {
        return  A[0]*A[0] + A[1]*A[1]
    }
    let resultArr = points.sort((a,b)=> {return fn(a) - fn(b)});
    return resultArr.splice(0,K)
};