LeetCode 447: Number of Boomerangs Solution

Master LeetCode problem 447 (Number of Boomerangs), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

447. Number of Boomerangs

Medium

Array Hash Table Math

Problem Explanation

Explanation:

We can solve this problem by iterating through each point and calculating the distances to all other points.
We will use a hashmap to store the count of distances for each point.
For each point, we calculate the distance to all other points and store them in the hashmap.
For any two points with the same distance, we can form a boomerang with the current point.
The number of boomerangs for a single point is calculated by choosing 2 points out of n, which is n*(n-1).
Finally, we sum up the number of boomerangs for each point to get the total count.

Time Complexity: O(n^2) - We iterate through all points and calculate distances to all other points. Space Complexity: O(n) - We use a hashmap to store distances for each point.

Solution Code

class Solution {
    public int numberOfBoomerangs(int[][] points) {
        int count = 0;
        for (int i = 0; i < points.length; i++) {
            Map<Integer, Integer> distances = new HashMap<>();
            for (int j = 0; j < points.length; j++) {
                if (i == j) continue;
                int dist = (int) (Math.pow(points[i][0] - points[j][0], 2) + Math.pow(points[i][1] - points[j][1], 2));
                distances.put(dist, distances.getOrDefault(dist, 0) + 1);
            }
            for (int val : distances.values()) {
                count += val * (val - 1);
            }
        }
        return count;
    }
}

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