# LeetCode Number of Boomerangs

LeetCode 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 iand 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 ans = 0;
for (int i = 0; i < points.size(); ++i) {
unordered_map<int, int> dist_cnt;
for (int j = 0; j < points.size(); ++j) {
int xdiff = points[i].first - points[j].first;
int ydiff = points[i].second - points[j].second;
++dist_cnt[xdiff*xdiff + ydiff*ydiff];
}
for (auto it = dist_cnt.begin(); it != dist_cnt.end(); ++it)ans += it->second*(it->second - 1);
}
return ans;
}
};