My idea starts from this example `n = 6`

and `k=5`

: `[1,6,2,5,3,4]`

If `k < n-1`

, I arrange the numbers increasing or decreasing from the k-th number.

```
def constructArray(self, n, k):
l, r, res = 2, n, [1]
for _ in range(k - 1):
if len(res) & 1:
res.append(r)
r -= 1
else:
res.append(l)
l += 1
if len(res) & 1:
res.extend(range(l, r + 1))
else:
res.extend(range(r, l - 1, -1))
return res
```