Description
Given a list of dominoes, return the number of pairs (i, j) for which i < j and dominoes[i] is equivalent to dominoes[j]. Dominoes are equivalent if one can be rotated to match the other.
Examples
Input:
dominoes = [[1,2],[2,1],[3,4],[5,6]]Output:
1Explanation:
[1,2] and [2,1] are equivalent.
Input:
dominoes = [[1]]Output:
1Explanation:
With only one domino, there are no pairs to compare.
Input:
dominoes = [[1,1],[2,3],[3,2],[1,1],[4,5]]Output:
2Explanation:
[1,1] at indices 0 and 3 form one equivalent pair. [2,3] at index 1 and [3,2] at index 2 are equivalent (another pair). Total: 2 pairs.
Constraints
- •
1 ≤ dominoes.length ≤ 4 * 10^4 - •
dominoes[i].length == 2