# Leetcode 447 - Number of Boomerangs

`Note:`

- Not a really good problem.
- For every
`point`

, build a map with`key = dist, val = point coords`

(val should be an array). - Math knowledge: For each pair, its val contains our
`j`

and`k`

. Assume the`length`

is`l`

, how many`combinations`

can we come up with? Itâ€™s`l * (l - 1)`

!

`Question:`

You are given `n`

`points`

in the plane that are all distinct, where `points[i] = [xi, yi]`

. A boomerang is a tuple of points `(i, j, k)`

such that the distance between `i`

and `j`

equals the distance between `i`

and `k`

(the order of the tuple matters).

Return the `number`

of boomerangs.

`Example:`

1 | Input: points = [[0,0],[1,0],[2,0]] |

`Code:`

1 | /** |