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N couples sit in 2N seats arranged in a row and want to hold hands. We want to know the minimum number of swaps so that every couple is sitting side by side. A swap consists of choosing any two people, then they stand up and switch seats.
The people and seats are represented by an integer from
2N-1, the couples are numbered in order, the first couple being
(0, 1), the second couple being
(2, 3), and so on with the last couple being
The couples' initial seating is given by
row[i] being the value of the person who is initially sitting in the i-th seat.
Input: row = [0, 2, 1, 3] Output: 1 Explanation: We only need to swap the second (row) and third (row) person.
Input: row = [3, 2, 0, 1] Output: 0 Explanation: All couples are already seated side by side.
len(row)is even and in the range of
rowis guaranteed to be a permutation of