1128. Number of Equivalent Domino Pairs-等价多米诺骨牌对的数量

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

Solution in python:

class Solution:
    def numEquivDominoPairs(self, dominoes: List[List[int]]) -> int:
        count = 0
        adic = dict()
        for item in dominoes:
            one = str(item[0])+','+str(item[1])
            two = str(item[1])+','+str(item[0])
            if (one not in adic.keys()) and (two not in adic.keys()):
                adic[one] = 0
            elif (one not in adic.keys()) and (two in adic.keys()):
                adic[two] += 1
            else:
                adic[one] += 1
        for v in adic.values():
            count += v*(v+1)//2
        return count