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]]
class Solution {
public:
int numberOfBoomerangs(vector<pair<int, int>>& points) {
int num = 0;
for (int i = 0; i < points.size(); i++) {
unordered_map<long, int> map(points.size());
for (int j = 0; j < points.size(); j++)
{
if (i == j) continue;
int dx = points[i].first - points[j].first;
int dy = points[i].second - points[j].second;
long key = dx*dx + dy*dy;
map[key]++;
}
for (auto& a : map)
{
if (a.second > 1)
{
num += a.second * (a.second-1);
}
}
}
return num;
}
};