题目

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 0 to 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 (2N-2, 2N-1).

The couples’ initial seating is given by row[i] being the value of the person who is initially sitting in the i-th seat.

Note:

1. len(row) is even and in the range of [4, 60].
2. row is guaranteed to be a permutation of 0…len(row)-1.

Example 1:
Input: row = [0, 2, 1, 3]
Output: 1
Explanation: We only need to swap the second (row[1]) and third (row[2]) person.

Example 2:
Input: row = [3, 2, 0, 1]
Output: 0
Explanation: All couples are already seated side by side.

C++代码

``````class Solution {
public:
int minSwapsCouples(vector<int>& row) {
int result = 0;
for (int i = 0; i < row.size(); i+=2)
{
if (row[i]/2 != row[i+1]/2)
{
for (int j = i+2; j < row.size(); j+=2)
{
int s = -1;
if (row[i]/2 == row[j]/2)
{
s = j;
}
else if (row[i]/2 == row[j+1]/2)
{
s = j+1;
}
if (s != -1)
{
int temp = row[i+1];
row[i+1] = row[s];
row[s] = temp;
result++;
break;
}
}
}
}
return result;
}
};
``````