973_K_Closest_Points_to_Origin.java

class Solution {
/*     public int[][] kClosest(int[][] points, int K) {
        // Sort
        int N = points.length;
        int[] dists = new int[N];
        for (int i = 0; i < N; ++i)
            dists[i] = dist(points[i]);

        Arrays.sort(dists);
        int distK = dists[K-1];

        int[][] ans = new int[K][2];
        int t = 0;
        for (int i = 0; i < N; ++i)
            if (dist(points[i]) <= distK)
                ans[t++] = points[i];
        return ans;
    } */

    private int dist(int[] point) {
        return point[0] * point[0] + point[1] * point[1];
    }

    public int[][] kClosest(int[][] points, int K) {
        // Min Heap with PriorityQueue
        PriorityQueue<int[]> pq = new PriorityQueue<int[]>((p1, p2) -> dist(p2) - dist(p1));
        for (int[] p : points) {
            pq.offer(p);
            if (pq.size() > K) {
                pq.poll();
            }
        }
        int[][] res = new int[K][2];
        while (K > 0) {
            res[--K] = pq.poll();
        }
        return res;
    }
}