Number of Equivalent Domino Pairs

Easy
1
40.0% Acceptance

In this lab, you will build a function that calculates the number of equivalent domino pairs. A pair of dominoes dominoes[i] = [a, b] is equivalent to dominoes[j] = [c, d] if and only if either (a == c and b == d) or (a == d and b == c). In other words, one domino can be rotated to be equal to another domino.

Your task is to create a function numEquivDominoPairs that takes an array of dominoes as input and returns the number of equivalent pairs (i, j) for which 0 <= i < j < dominoes.length and dominoes[i] is equivalent to dominoes[j].

Example 1:

const dominoes = [ [1, 2], [2, 1], [3, 4], [5, 6], ]; console.log(numEquivDominoPairs(dominoes)); // Output: 1

Example 2:

const dominoes = [ [1, 2], [1, 2], [1, 1], [1, 2], [2, 2], ]; console.log(numEquivDominoPairs(dominoes)); // Output: 3

Constraints:

  • 1 <= dominoes.length <= 4 * 104
  • dominoes[i].length == 2
  • 1 <= dominoes[i][j] <= 9

Challenges

  1. Export the function numEquivDominoPairs from index.js.
  2. Implement the function numEquivDominoPairs such that it passes the given test cases and any additional tested cases.