Title
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]]
题目大意。。。用的map存储长度和此长度的个数
Solution
//cpp:
class Solution {
public:
int numberOfBoomerangs(vector<pair<int, int>>& points) {
int res = 0;
for (int i = 0; i < points.size(); i++) {
unordered_map<long, int> map1;
for (int j = 0; j < points.size(); j++) {
if (j == i)
continue;
int dy = points[i].second - points[j].second;
int dx = points[i].first - points[j].first;
long key = dx * dx + dy * dy;
map1[key]++;
}
for (auto p : map1) {
if (p.second > 1) {
res += p.second*(p.second - 1);
}
}
}
return res;
}
};