​LeetCode刷题实战447：回旋镖的数量

示例 1：
输入：points = [[0,0],[1,0],[2,0]]

输出：2
解释：两个回旋镖为 [[1,0],[0,0],[2,0]] 和 [[1,0],[2,0],[0,0]]

示例 2：
输入：points = [[1,1],[2,2],[3,3]]
输出：2

示例 3：
输入：points = [[1,1]]
输出：0

class Solution {
    public static int numberOfBoomerangs(int[][] points) {
        int len=points.length;
        int res=0;
        HashMap hashMap=new HashMap();
        for(int i=0;i            for(int j=0;j                if(i!=j){
                    int x=points[i][0]-points[j][0];
                    int y=points[i][1]-points[j][1];
                    int dist=x*x+y*y;
                    if(hashMap.containsKey(dist)){
                        hashMap.put(dist,hashMap.get(dist)+1);
                    }else{
                        hashMap.put(dist,1);
                    }
                }
            }
            for(Integer count:hashMap.values()){
                res+=count*(count-1);
            }
            hashMap.clear();
        }
        return res;
    }
}