public int numberOfBoomerangs(int[][] points) {

int count = 0;

for (int[] middle: points) {

// 记录每个其他点到这个点的距离，如果距离相同的点有n个，则回旋标的个数是n中选2个的种类数

Map<Double, Integer> map = new HashMap<>();

for (int[] point: points) {

if (point[0] == middle[0] && point[1] == middle[1]) {

// 相同点忽略

continue;

}

double distance = distance(middle, point);

map.put(distance, map.getOrDefault(distance, 0) + 1);

}

// 计算个数

for (double distance : map.keySet()) {

count += map.get(distance) * (map.get(distance) - 1);

}

}

return count;

}

// 暴力遍历，超时

public int numberOfBoomerangs1(int[][] points) {

int count = 0;

for (int[] middle: points) {

for (int[] left: points) {

if (left[0] == middle[0] && left[1] == middle[1]) {

// 相同点忽略

continue;

}

double distance = distance(middle, left);

for (int[] right: points) {

if (left[0] == right[0] && left[1] == right[1]) {

// 相同点忽略

continue;

}

if (distance(middle, right) == distance) {

count++;

}

}

}

}

return count;

}

private double distance(int[] point1, int[] point2) {

return Math.pow((point1[0] -point2[0]), 2.0) + Math.pow((point1[1] -point2[1]), 2);

}