0059. Spiral Matrix II

class Solution {

    // public int[] rMove = new int{0, 1, 0, -1};
    // public int[] cMove = new int{1, 0, -1, 0};

    public static void helper(int shuffle, int[][] res, int val, int r, int c, int side, int n, boolean odd) {
        if (side == 1 || side == 0) {
            return;
        }
        else {
            // dir == 0, right
            if (shuffle == 0) {
                int j = c;
                while (j < c + side) {
                    res[r][j] = val;
                    val++;
                    j++;
                }
                helper(1, res, val, r, j, side, n, odd);
            }
            // dir == 1, down
            else if (shuffle == 1) {
                int i = r;
                while (i < r + side) {
                    res[i][c] = val;
                    i++;
                    val++;
                }
                helper(2, res, val, i, c, side, n, odd);
            }
            // dir == 2, left
            else if (shuffle == 2) {
                int j = c;
                while (j > c - side) {
                    res[r][j] = val;
                    j--;
                    val++;
                }
                helper(3, res, val, r, j, side, n, odd);
            }
            // dir == 3, up (side - 1, r + 1, c + 1)
            else if (shuffle == 3) {
                int i = r;
                while (i > r - side) {
                    res[i][c] = val;
                    i--;
                    val++;
                }
                helper(0, res, val, i + 1, c + 1, side - 2, n, odd);
            }
        }
    }



    public static int[][] generateMatrix(int n){
        int[][] res = new int[n][n];
        if (n % 2 == 1) {
            res[n / 2][n / 2] = n * n;
        }
        else if (n % 2 == 0) {
            res[n / 2 - 1][n / 2 - 1] = n * n - 3;
            res[n / 2 - 1][n / 2] = n * n - 2;
            res[n / 2][n / 2] = n * n - 1;
            res[n / 2][n / 2 - 1] = n * n;
        }
        if (n > 2) {
            helper(0, res, 1, 0, 0, n - 1, n, n % 2 == 1);
        }
        return res;
    }
}