973. K Closest Points to Origin

Question

We have a list of points on the plane. Find the K closest points to the origin (0, 0).

(Here, the distance between two points on a plane is the Euclidean distance.)

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

Note:

1 <= K <= points.length <= 10000
-10000 < points[i][0] < 10000
-10000 < points[i][1] < 10000

Solutions:

Method 1: PriorityQueue

class Solution {
    public int[][] kClosest(int[][] points, int K) {
        PriorityQueue<int[]> pq = new PriorityQueue<>(new Comparator<int[]>(){
            @Override
            public int compare(int[] a, int[] b){
                return a[0] * a[0] + a[1] * a[1] - b[0] * b[0] - b[1] * b[1];
            }
        });
        for(int[] point : points)   pq.offer(point);
        int[][] res = new int[K][2];
        int count = 0;
        for(int i = 0; i < K; i++){
            res[i] = pq.poll();
        }
        return res;
    }
}