# Number of Boomerangs in Python

PythonServer Side ProgrammingProgramming

Suppose we have n points in the plane that are all pairwise distinct. Now a "boomerang" is a tuple of points like (i, j, k) such that the distance between i and j is the same as the distance between i and k. We have to find the number of boomerangs.

So, if the input is like [[0,0],[1,0],[2,0]], then the output will be 2, as two boomerangs are [[1,0],[0,0],[2,0]] and [[1,0],[2,0],[0,0]].

To solve this, we will follow these steps −

• counter_of_boomerangs := 0

• for each point_1 in points array, do

• x1, y1 = point_1

• define a map called distance_count_dict

• for each point_2 in points array, do

• x2, y2 = point_2

• diff_x := x2 - x1

• diff_y := y2 - y1

• dist := diff_x^2 + diff_y^2

• distance_count_dict[ dist ] := distance_count_dict[ dist ] + 1

• for each d in distance_count_dict −

• n := distance_count_dict[d]

• counter_of_boomerangs := counter_of_boomerangs + n * (n - 1)

• return counter_of_boomerangs

## Example

Let us see the following implementation to get better understanding −

Live Demo

from collections import defaultdict
class Solution:
def numberOfBoomerangs(self, points):
counter_of_boomerangs = 0
for point_1 in points:
x1, y1 = point_1
distance_count_dict = defaultdict( int )
for point_2 in points:
x2, y2 = point_2
diff_x = x2-x1
diff_y = y2-y1
dist = diff_x ** 2 + diff_y ** 2
distance_count_dict[ dist ] += 1
for d in distance_count_dict:
n = distance_count_dict[d]
counter_of_boomerangs += n * (n-1)
return counter_of_boomerangs

ob = Solution()
print(ob.numberOfBoomerangs([[0,0],[1,0],[2,0]]))

## Input

[[0,0],[1,0],[2,0]]

## Output

0
Published on 10-Jun-2020 16:18:55