447. Number of Boomerangs

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LeetCode

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Problem

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: 2
Explanation: 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.

Code

class Solution {
    public int numberOfBoomerangs(int[][] points) {
        int res = 0;
        
        for(int i = 0; i < points.length; i++){
            HashMap<Integer, Integer> map = new HashMap<>();
            
            for(int j = 0; j < points.length; j++){
                int dist = helper(points[i], points[j]);
                map.put(dist, map.getOrDefault(dist, 0) + 1);
            }
            
            for(int val : map.values()){
                res += val *  (val - 1);
            }
        }
        
        return res;
    }
    
    private int helper(int[] p1, int[] p2){
        int x = p1[0] - p2[0];
        int y = p1[1] - p2[1];
        
        return x * x + y * y;
    }
}