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]]
Output: 1

Constraints:

• 1 <= dominoes.length <= 40000
• 1 <= dominoes[i][j] <= 9

# @lc code=start
using LeetCode

function num_equiv_domino_pairs(dominoes::Vector{Tuple{Int,Int}})::Int
    counts = Dict{Tuple{Int,Int},Int}()
    n = 0
    for (k, v) in dominoes
        p = minmax(k, v)
        if haskey(counts, p)
            n += counts[p]
            counts[p] += 1
        else
            counts[p] = 1
        end
    end
    return n
end
# @lc code=end

num_equiv_domino_pairs (generic function with 1 method)

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