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
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