1128. 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|1,2],[2,1],[3,4],[5,6]]
Output: 1

Example 2:

Input: dominoes = [[1,2],[1,2],[1,1],[1,2],[2,2|1,2],[1,2],[1,1],[1,2],[2,2]]
Output: 3

def numEquivDominoPairs(self, dominoes: List[List[int]]) -> int:
	count = [0] * 100  
	result = 0
	for a, b in dominoes:
		key = a * 10 + b if a <= b else b * 10 + a
		result += count[key]
		count[key] += 1
	return result