LeetCode: Spiral Matrix II Solution

Same with I, with a small modification

Approach

Traverse the empty matrix and assign values

Implementation

1var generateMatrix = function (n) {
2  const res = Array.from({ length: n }, _ => Array(n).fill(false))
3  const DIR = {
4    R: 0,
5    D: 1,
6    L: 2,
7    U: 3,
8  }
9
10  let el = 1
11
12  const isValidCell = (i, j) => 0 <= i && i < n && 0 <= j && j < n && !res[i][j]
13
14  const recursion = (i, j, dir) => {
15    if (!isValidCell(i, j)) {
16      dir === DIR.R &&
17        isValidCell(i + 1, j - 1) &&
18        recursion(i + 1, j - 1, DIR.D)
19      dir === DIR.D &&
20        isValidCell(i - 1, j - 1) &&
21        recursion(i - 1, j - 1, DIR.L)
22      dir === DIR.L &&
23        isValidCell(i - 1, j + 1) &&
24        recursion(i - 1, j + 1, DIR.U)
25      dir === DIR.U &&
26        isValidCell(i + 1, j + 1) &&
27        recursion(i + 1, j + 1, DIR.R)
28      return
29    }
30
31    res[i][j] = el++
32
33    dir === DIR.R && recursion(i, j + 1, dir)
34    dir === DIR.D && recursion(i + 1, j, dir)
35    dir === DIR.L && recursion(i, j - 1, dir)
36    dir === DIR.U && recursion(i - 1, j, dir)
37  }
38
39  recursion(0, 0, DIR.R)
40
41  return res
42}