Number of Equivalent Domino Pairs
Easy
You receive a list 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 ) - that is, one domino can be rotated to be equal to another domino.
Find and provide the count of pairs (i, j) for which 0 <= i < j < dominoes.length, and dominoes[i] is equivalent to dominoes[j].
Example 1
Input: dominoes = [[1,2],[2,1],[3,4],[5,6]]
Output: 1
Example 2
Input: dominoes = [[1,2],[1,2],[1,1],[1,2],[2,2]]
Output: 3
Constraints
1 <= dominoes.length <= 4 * 10^4dominoes[i].length == 21 <= dominoes[i][j] <= 9
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