Count Boomerangs

Problem

Count the ordered triples (i, j, k) of distinct points where the distance from i to j equals the distance from i to k, making i the boomerang tip.

For each point i, group all squared distances to the other points and add c * (c - 1) for every distance with count c. Squared distances avoid floating point errors.

Hint

For a fixed tip, any two points at the same distance form two ordered boomerangs.

Test cases

case 1

in: [[[0,0],[1,0],[2,0]]]

expected: 2

case 2

in: [[[1,1],[1,1],[1,1]]]

expected: 6

case 3

in: [[[0,0],[1,0]]]

expected: 0

case 4

in: [[[1,1],[2,2],[3,3]]]

expected: 2

Starter codePython

def count_boomerangs(points):
    # Your code here
    pass

4 test cases · run your code against them in the editor