leetcode447. Number of Boomerangs

You are given n points in the plane that are all distinct, where points[i] = [xi, yi]. A boomerang is a tuple of points (i, j, k) such that the distance between i and j equals the distance between i and k (the order of the tuple matters).

Return the number of boomerangs.

Example 1:

Input: points = [[0,0],[1,0],[2,0]]Output: 2Explanation: The two boomerangs are [[1,0],[0,0],[2,0]] and [[1,0],[2,0],[0,0]].

Example 2:

Input: points = [[1,1],[2,2],[3,3]]Output: 2

Example 3:

Input: points = [[1,1]]Output: 0

Constraints:

• n == points.length

• 1 <= n <= 500

• points[i].length == 2

• -104 <= xi, yi <= 104

• All the points are unique.

  一个函数计算2个点的尺寸，然后2个循环算出所有点之间的尺寸，map存储，然后根据相同数量，就能算出来

Runtime: 187 ms, faster than 65.29% of Java online submissions for Number of Boomerangs.

Memory Usage: 109.6 MB, less than 68.56% of Java online submissions for Number of Boomerangs.