# K Closest Points

## Problem

### Description

Given some points and a point origin in two dimensional space, find k points out of the some points which are nearest to origin. Return these points sorted by distance, if they are same with distance, sorted by x-axis, otherwise sorted by y-axis.

#### Example

Given points = [[4,6],[4,7],[4,4],[2,5],[1,1]], origin = [0, 0], k = 3 return [[1,1],[2,5],[4,4]]

## 题解

### Java

/**
* Definition for a point.
* class Point {
*     int x;
*     int y;
*     Point() { x = 0; y = 0; }
*     Point(int a, int b) { x = a; y = b; }
* }
*/

public class Solution {
/**
* @param points: a list of points
* @param origin: a point
* @param k: An integer
* @return: the k closest points
*/
public Point[] kClosest(Point[] points, Point origin, int k) {
Queue<Point> heap = new PriorityQueue<Point>(new DistanceComparator(origin));
for (Point point : points) {
if (heap.size() < k) {
heap.offer(point);
} else {
Point peek = heap.peek();
if (distance(peek, origin) <= distance(point, origin)) {
continue;
} else {
heap.poll();
heap.offer(point);
}
}
}

int minK = Math.min(k, heap.size());
Point[] kClosestPoints = new Point[minK];
for (int i = 1; i <= minK; i++) {
kClosestPoints[minK - i] = heap.poll();
}

return kClosestPoints;
}

public int distance(Point p, Point origin) {
return (p.x - origin.x) * (p.x - origin.x) +
(p.y - origin.y) * (p.y - origin.y);
}

class DistanceComparator implements Comparator<Point> {
private Point origin = null;
public DistanceComparator(Point origin) {
this.origin = origin;
}

public int compare(Point p1, Point p2) {
int d1 = distance(p1, origin);
int d2 = distance(p2, origin);
if (d1 != d2) {
return d2 - d1;
} else {
if (p1.x != p2.x) {
return p2.x - p1.x;
} else {
return p2.y - p1.y;
}
}
}
}
}