612 - K个最近的点

2017.10.30

就是先算出每个点到目标点的距离，然后按距离排序。

当距离相等的时候，按照x，y的值进行排序。

最后，输出前k个就可以了。

/**
 * 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) {
        // write your code here
		HashMap<Integer,LinkedList<Point>> map = new HashMap<>();
		for(Point p : points){
			//System.out.println("Point p = [" + p.x + "," + p.y +"]" );
			int distance = getDistance(p,origin);
			if(!map.containsKey(distance) == true){
				LinkedList<Point> list = new LinkedList<>();
				list.add(p);
				map.put(distance, list);
			}
			else{
				map.get(distance).add(p);
			}
		}
		//printMap(map);
		int[] key = new int[map.keySet().size()];
		int tmp = 0;
		for(int i : map.keySet()){
			key[tmp++] = i;
		}
		Arrays.sort(key);
		//System.out.println("zheli");
		int count = 0;
		Point[] res = new Point[k];
		for(int i = 0 ; i < key.length; i++){
			LinkedList<Point> listTmp = map.get(key[i]);
			listTmp = sort(listTmp);
			for(Point p :listTmp){
				res[count] = p;
				//System.out.println("加入[" + p.x + "," + p.y +"]" );
				count++;
				if(count >= k){	
					return res;
				}
			}
		}
		return res;
    }
	public LinkedList<Point> sort(LinkedList<Point> list){
		if(list.isEmpty() || list.size() == 1){
			return list;
		}
		LinkedList<Point> res = new LinkedList<>();
		for(Point p : list){
			if(res.isEmpty()){
				res.add(p);
			}
			else{
			    res.add(p);
				 for(int i = res.size() - 2; i >= 0; i--){
					Point p2 = res.get(i);
						if(p.x > p2.x){
						    continue;
						}
						if(p.x == p2.x && p.y >= p2.y){
						    continue;
						}
						res.set(i+1, p2);
						if(p.x < p2.x){
							res.set(i,p);
						}
						else if(p.x == p2.x && p.y <= p2.y){
							res.set(i,p);
						}
				}
			}
		}
		return res;
	}
		public int getDistance(Point point, Point origin) {
        // write your code here
		int a = point.x - origin.x;
		int b = point.y - origin.y;
		return a*a + b*b;
    }
}