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.
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.
Note:
len(row)
is even and in the range of [4, 60]
.row
is guaranteed to be a permutation of 0...len(row)-1
.struct Solution;
impl Solution {
fn min_swaps_couples(mut row: Vec<i32>) -> i32 {
let n = row.len();
let mut res = 0;
for i in 0..n {
if i % 2 == 1 {
continue;
}
if row[i] == row[i + 1] ^ 1 {
continue;
}
res += 1;
for j in i + 2..n {
if row[i] == row[j] ^ 1 {
row.swap(i + 1, j);
break;
}
}
}
res
}
}
#[test]
fn test() {
let row = vec![0, 2, 1, 3];
let res = 1;
assert_eq!(Solution::min_swaps_couples(row), res);
let row = vec![3, 2, 0, 1];
let res = 0;
assert_eq!(Solution::min_swaps_couples(row), res);
}