## 667. Beautiful Arrangement II

Given two integers `n` and `k`, you need to construct a list which contains `n` different positive integers ranging from `1` to `n` and obeys the following requirement:
Suppose this list is [a1, a2, a3, ... , an], then the list [|a1 - a2|, |a2 - a3|, |a3 - a4|, ... , |an-1 - an|] has exactly `k` distinct integers.

If there are multiple answers, print any of them.

Example 1:

```Input: n = 3, k = 1
Output: [1, 2, 3]
Explanation: The [1, 2, 3] has three different positive integers ranging from 1 to 3, and the [1, 1] has exactly 1 distinct integer: 1.
```

Example 2:

```Input: n = 3, k = 2
Output: [1, 3, 2]
Explanation: The [1, 3, 2] has three different positive integers ranging from 1 to 3, and the [2, 1] has exactly 2 distinct integers: 1 and 2.
```

Note:

1. The `n` and `k` are in the range 1 <= k < n <= 104.

## Rust Solution

``````struct Solution;

impl Solution {
fn construct_array(n: i32, mut k: i32) -> Vec<i32> {
let mut res = vec!;
let mut l = 2;
let mut r = n;
let mut forward = true;
for _ in 1..n {
if k > 1 {
if forward {
res.push(r);
r -= 1;
} else {
res.push(l);
l += 1;
}
forward = !forward;
k -= 1;
} else {
if forward {
res.push(l);
l += 1;
} else {
res.push(r);
r -= 1;
}
}
}
res
}
}

#[test]
fn test() {
let n = 3;
let k = 1;
let res = vec![1, 2, 3];
assert_eq!(Solution::construct_array(n, k), res);
let n = 3;
let k = 2;
let res = vec![1, 3, 2];
assert_eq!(Solution::construct_array(n, k), res);
let n = 5;
let k = 2;
let res = vec![1, 5, 4, 3, 2];
assert_eq!(Solution::construct_array(n, k), res);
}
``````

Having problems with this solution? Click here to submit an issue on github.