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Number of Equivalent Domino Pairs

Given 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...

Given 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.

Return the number 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 * 10^4
  • dominoes[i].length == 2
  • 1 <= dominoes[i][j] <= 9

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