struct Solution;
impl Solution {
fn count_arrangement(n: i32) -> i32 {
let mut res = 0;
let mut nums = (1..=n).collect();
let n = n as usize;
Self::dfs(0, &mut nums, &mut res, n);
res
}
fn dfs(start: usize, nums: &mut Vec<i32>, all: &mut i32, n: usize) {
if start == n {
*all += 1;
} else {
for i in start..n {
if nums[i] % (start as i32 + 1) == 0 || (start as i32 + 1) % nums[i] == 0 {
nums.swap(start, i);
Self::dfs(start + 1, nums, all, n);
nums.swap(start, i);
}
}
}
}
}
#[test]
fn test() {
let n = 2;
let res = 2;
assert_eq!(Solution::count_arrangement(n), res);
}