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 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

Constraints:

• 1 <= dominoes.length <= 40000

• 1 <= dominoes[i][j] <= 9

def numEquivDominoPairs(self, dominoes: List[List[int]]) -> int:
        mp = {}
        count = 0
        for i in range(0, len(dominoes)):
            add = dominoes[i][0] + dominoes[i][1]
            sub = abs(dominoes[i][0] - dominoes[i][1])
            s = str(add) + "," + str(sub)
            if (s in mp):
                count = count + 1 + mp[s]
                mp[s] += 1
            else:
                mp[s] = 0
        return count