34. leetcode 447. Number of Boomerangs
Given n points in the plane that are all pairwise distinct, 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).
Find the number of boomerangs. You may assume that n will be at most 500 and coordinates of points are all in the range [-10000, 10000] (inclusive).
Example:
Input:
[[0,0],[1,0],[2,0]]
Output:
2
Explanation:
The two boomerangs are [[1,0],[0,0],[2,0]] and [[1,0],[2,0],[0,0]]
思路:对于每一个点P,求它和其它点的距离,若存在n个点与P的距离为d,则可构成n*(n-1)个三元组(n大于1)。利用C++ 的map,依次遍历每一个点。