447. 回旋镖的数量

447. 回旋镖的数量

• 难度: medium
• 原始链接: https://leetcode.cn/problems/number-of-boomerangs
• 标签: 哈希

解法一: 哈希

go

func numberOfBoomerangs(points [][]int) int {
    ans := 0
    for _, point1 := range points {
        distanceHash := make(map[int]int)
        for _, point2 := range points {
            distanceHash[(point2[0] - point1[0]) * (point2[0] - point1[0]) + (point2[1] - point1[1]) * (point2[1] - point1[1])]++
        }
        for _, count := range distanceHash {
            if count > 1 {
                ans += count * (count - 1)
            }
        }
    }
    return ans
}

java

class Solution {
    public int numberOfBoomerangs(int[][] points) {
        int ans = 0;
        Map<Integer, Integer> distanceHash = new HashMap<>();
        for (int[] point1 : points) {
            distanceHash.clear();
            for (int[] point2 : points) {
                int distance = (point2[0] - point1[0]) * (point2[0] - point1[0]) + (point2[1] - point1[1]) * (point2[1] - point1[1]);
                distanceHash.put(distance, distanceHash.getOrDefault(distance, 0) + 1);
            }
            for (Map.Entry<Integer, Integer> entry : distanceHash.entrySet()) {
                int count = entry.getValue();
                ans += (count - 1) * count;
            }
        }
        return ans;
    }
}